Cell wall modifications by α-XYLOSIDASE1 are required for control of seed and fruit size in Arabidopsis.

Cell wall modifications are of pivotal importance during plant development. Among cell wall components, xyloglucans are the major hemicellulose polysaccharide in primary cell walls of dicots and non-graminaceous monocots. They can connect the cellulose microfibril surface to affect cell wall mechanical properties. Changes in xyloglucan structure are known to play an important role in regulating cell growth. Therefore, the degradation of xyloglucan is an important modification that alters the cell wall. The α-XYLOSIDASE1 (XYL1) gene encodes the only α-xylosidase acting on xyloglucans in Arabidopsis thaliana. Here, we showed that mutation of XYL1 strongly influences seed size, seed germination, and fruit elongation. We found that the expression of XYL1 is directly regulated in developing seeds and fruit by the MADS-box transcription factor SEEDSTICK. We demonstrated that XYL1 complements the stk smaller seed phenotype. Finally, by atomic force microscopy, we investigated the role of XYL1 activity in maintaining cell stiffness and growth, confirming the importance of cell wall modulation in shaping organs.

Xyloglucan exoglycosidases in the monocot model Brachypodium distachyon and the conservation of xyloglucan disassembly in angiosperms.

KEY MESSAGE: Brachypodium distachyon has a full set of exoglycosidases active on xyloglucan, including α-xylosidase, ß-galactosidase, soluble and membrane-bound ß-glucosidases and two α-fucosidases. However, unlike in Arabidopsis, both fucosidases are likely cytosolic. Xyloglucan is present in primary walls of all angiosperms. While in most groups it regulates cell wall extension, in Poaceae its role is still unclear. Five exoglycosidases participate in xyloglucan hydrolysis in Arabidopsis: α-xylosidase, ß-galactosidase, α-fucosidase, soluble ß-glucosidase and GPI-anchored ß-glucosidase. Mutants in the corresponding genes show alterations in xyloglucan composition. In this work putative orthologs in the model grass Brachypodium distachyon were tested for their ability to complement Arabidopsis mutants. Xylosidase and galactosidase mutants were complemented, respectively, by BdXYL1 (Bd2g02070) and BdBGAL1 (Bd2g56607). BdBGAL1, unlike other xyloglucan ß-galactosidases, is able to remove both galactoses from XLLG oligosaccharides. In addition, soluble ß-glucosidase BdBGLC1 (Bd1g08550) complemented a glucosidase mutant. Closely related BdBGLC2 (Bd2g51280), which has a putative GPI-anchor sequence, was found associated with the plasma membrane and only a truncated version without GPI-anchor complemented the mutant, proving that Brachypodium also has soluble and membrane-bound xyloglucan glucosidases. Both BdXFUC1 (Bd3g25226) and BdXFUC2 (Bd1g28366) can hydrolyze fucose from xyloglucan oligosaccharides but were unable to complement a fucosidase mutant. Fluorescent protein fusions of BdXFUC1 localized to the cytosol and both proteins lack a signal peptide. Signal peptides appear to have evolved only in some eudicot lineages of this family, like the one leading to Arabidopsis. These results could be explained if cytosolic xyloglucan α-fucosidases are the ancestral state in angiosperms, with fucosylated oligosaccharides transported across the plasma membrane.

Analysis of Xyloglucan Composition in Arabidopsis Leaves.

Xyloglucan is one of the main components of the primary cell wall in most species of plants. This protocol describes a method to analyze the composition of the enzyme-accessible and enzyme-inaccessible fractions of xyloglucan in the model species Arabidopsis thaliana. It is based on digestion with an endoglucanase that attacks unsubstituted glucose residues in the backbone. The identities and relative amounts of released xyloglucan fragments are then determined using MALDI-TOF mass spectrometry.

Soluble and Membrane-Bound ß-Glucosidases Are Involved in Trimming the Xyloglucan Backbone.

In many flowering plants, xyloglucan is a major component of primary cell walls, where it plays an important role in growth regulation. Xyloglucan can be degraded by a suite of exoglycosidases that remove specific sugars. In this work, we show that the xyloglucan backbone, formed by (1→4)-linked ß-d-glucopyranosyl residues, can be attacked by two different Arabidopsis (Arabidopsis thaliana) ß-glucosidases from glycoside hydrolase family 3. While BGLC1 (At5g20950; for ß-glucosidase active against xyloglucan 1) is responsible for all or most of the soluble activity, BGLC3 (At5g04885) is usually a membrane-anchored protein. Mutations in these two genes, whether on their own or combined with mutations in other exoglycosidase genes, resulted in the accumulation of partially digested xyloglucan subunits, such as GXXG, GXLG, or GXFG. While a mutation in BGLC1 had significant effects on its own, lack of BGLC3 had only minor effects. On the other hand, double bglc1 bglc3 mutants revealed a synergistic interaction that supports a role for membrane-bound BGLC3 in xyloglucan metabolism. In addition, bglc1 bglc3 was complemented by overexpression of either BGLC1 or BGLC3 In overexpression lines, BGLC3 activity was concentrated in a microsome-enriched fraction but also was present in soluble form. Finally, both genes were generally expressed in the same cell types, although, in some cases, BGLC3 was expressed at earlier stages than BGLC1 We propose that functional specialization could explain the separate localization of both enzymes, as a membrane-bound ß-glucosidase could specifically digest soluble xyloglucan without affecting the wall-bound polymer.

Supervised physical exercise improves VO2max, quality of life, and health in early stage breast cancer patients: a randomized controlled trial.

Breast cancer patients suffer impairment in cardiorespiratory fitness after treatment for primary disease, affecting patients' health and survival. The aim of this study was to evaluate the ability of a pragmatic exercise intervention to improve cardiorespiratory fitness of breast cancer patients after primary treatment. Between February 2013 and December 2014, 94 women with early stage (I-III) breast cancer, 1-36 months post-chemotherapy, and radiotherapy were randomly assigned to an intervention program (EX) combining supervised aerobic and resistance exercise (n = 44) or usual care (CON) (n = 45) for 12 weeks. Primary study endpoint was VO2max. Secondary endpoints were muscle strength, shoulder range of motion, body composition, and quality of life (QoL). Assessments were undertaken at baseline, 12-week, and 6-month follow-ups. Eighty-nine patients aged 29-69 years were assessed at baseline and 12 weeks. The EX group showed significant improvements in VO2max, muscle strength, percent fat, and lean mass (p ≤ 0.001 in all cases) and QoL compared with usual care (CON). Apart from body composition, improvements were maintained for the EX at 6-month follow-up. There were no adverse events during the testing or exercise intervention program. A combined exercise intervention produced considerable improvement in cardiorespiratory fitness, physical function, and quality of life in breast cancer patients previously treated with chemotherapy and radiation therapy. Importantly, most of these benefits were maintained 6 months after ceasing the supervised exercise intervention.

Evolutionary divergence of ß-expansin structure and function in grasses parallels emergence of distinctive primary cell wall traits.

Expansins are wall-loosening proteins that promote the extension of primary cell walls without the hydrolysis of major structural components. Previously, proteins from the EXPA (α-expansin) family were found to loosen eudicot cell walls but to be less effective on grass cell walls, whereas the reverse pattern was found for EXPB (ß-expansin) proteins obtained from grass pollen. To understand the evolutionary and structural bases for the selectivity of EXPB action, we assessed the extension (creep) response of cell walls from diverse monocot families to EXPA and EXPB treatments. Cell walls from Cyperaceae and Juncaceae (families closely related to grasses) displayed a typical grass response ('ß-response'). Walls from more distant monocots, including some species that share with grasses high levels of arabinoxylan, responded preferentially to α-expansins ('α-response'), behaving in this regard like eudicots. An expansin with selective activity for grass cell walls was detected in Cyperaceae pollen, coinciding with the expression of genes from the divergent EXPB-I branch that includes grass pollen ß-expansins. The evolutionary origin of this branch was located within Poales on the basis of phylogenetic analyses and its association with the 'sigma' whole-genome duplication. Accelerated evolution in this branch has remodeled the protein surface in contact with the substrate, potentially for binding highly substituted arabinoxylan. We propose that the evolution of the divergent EXPB-I group made a fundamental change in the target and mechanism of wall loosening in the grass lineage possible, involving a new structural role for xylans and the expansins that target them.

Integrative exercise and lifestyle intervention increases leisure-time activity in breast cancer patients.

BACKGROUND: Physical activity has been demonstrated to increase survival in breast cancer patients, but few breast cancer patients meet the general recommendations for physical activity. The aim of this pilot study was to investigate if a supervised integrated counseling and group-based exercise program could increase leisure-time activity in women with breast cancer. METHODS: This pilot project, designed as a single-arm study with pre-post testing, consisted of 24 classes of combined aerobic and strength exercise training as well as classes on dietary and health behavior. A total of 48 women with breast cancer who were undergoing or had recently completed anticancer treatment completed the study. Leisure-time physical activity, grip strength, functional capacity, quality of life (QoL), and depression were assessed at baseline, after intervention, and at the 12-week follow-up after intervention. RESULTS: The breast cancer patients increased their leisure-time physical activity (P = .004), global strength (P = .004), functional capacity (P = .001), and QoL (P = .009), and their depression score (P = .004) significantly decreased. These improvements were independent of whether the patients were in ongoing therapy or had completed their treatment. CONCLUSION: This integrated intervention may produce lifestyle changes in breast cancer patients and survivors using the teachable moment to increase their leisure-time physical activity and, thereby, their QoL.

The role of basic psychological needs in predicting dispositional flow of basketball players in training. Differences by sex

Los objetivos del presente estudio fueron: a) analizar la influencia de la satisfacción de las necesidades psicológicas básicas sobre el flow disposicional en deportistas en formación y b) estudiar posibles diferencias en la explicación de esta relación según el género de los participantes. Se administraron los cuestionarios PNSE y FFS a 131 jugadores de baloncesto en formación. Los resultados indicaron que: a) los chicos mostraron niveles superiores de autonomía que las chicas; b) la competencia emergió como predictor del flow en ambas muestras; c) en los chicos, la autonomía también fue un predictor del flow (AU)

The objectives of this study were: a) analyze the influence of the satisfaction of basic psychological needs on dispositional flow in athletes in training and b) to study possible differences in the explanation of this relationship by sex of the participants. Questionnaires PNSE and FFS were administered to 131 basketball players in training. Results indicated that: a) boys showed higher levels of autonomy than girls; b) competence emerged as a predictor of flow in both samples, c) among boys, autonomy was also a predictor of flow (AU)

Regulation of secondary wall synthesis and cell death by NAC transcription factors in the monocot Brachypodium distachyon.

In several dicotyledonous species, NAC transcription factors act as master switches capable of turning on programmes of secondary cell-wall synthesis and cell death. This work used an oestradiol-inducible system to overexpress the NAC transcription factor BdSWN5 in the monocot model Brachypodium distachyon. This resulted in ectopic secondary cell-wall formation in both roots and shoots. Some of the genes upregulated in the process were a secondary cell-wall cellulose synthase (BdCESA4), a xylem-specific protease (BdXCP1) and an orthologue of AtMYB46 (BdMYB1). While activation of BdMYB1 may not be direct, this study showed that BdSWN5 is capable of transactivating the BdXCP1 promoter through two conserved binding sites. In the course of Brachypodium development, the BdXCP1 promoter was observed to be active in all types of differentiating tracheary elements. Together, these results suggest that Brachypodium SWNs can act as switches that turn on secondary cell-wall synthesis and programmed cell death.

AtBGAL10 is the main xyloglucan ß-galactosidase in Arabidopsis, and its absence results in unusual xyloglucan subunits and growth defects.

In growing cells, xyloglucan is thought to connect cellulose microfibrils and regulate their separation during wall extension. In Arabidopsis (Arabidopsis thaliana), a significant proportion of xyloglucan side chains contain ß-galactose linked to α-xylose at O2. In this work, we identified AtBGAL10 (At5g63810) as the gene responsible for the majority of ß-galactosidase activity against xyloglucan. Xyloglucan from bgal10 insertional mutants was found to contain a large proportion of unusual subunits, such as GLG and GLLG. These subunits were not detected in a bgal10 xyl1 double mutant, deficient in both ß-galactosidase and α-xylosidase. Xyloglucan from bgal10 xyl1 plants was enriched instead in XXLG/XLXG and XLLG subunits. In both cases, changes in xyloglucan composition were larger in the endoglucanase-accessible fraction. These results suggest that glycosidases acting on nonreducing ends digest large amounts of xyloglucan in wild-type plants, while plants deficient in any of these activities accumulate partly digested subunits. In both bgal10 and bgal10 xyl1, siliques and sepals were shorter, a phenotype that could be explained by an excess of nonreducing ends leading to a reinforced xyloglucan network. Additionally, AtBGAL10 expression was examined with a promoter-reporter construct. Expression was high in many cell types undergoing wall extension or remodeling, such as young stems, abscission zones, or developing vasculature, showing good correlation with α-xylosidase expression.

DVL genes play a role in the coordination of socket cell recruitment and differentiation.

Specialized plant cells arise from undifferentiated cells through a series of developmental steps. The decision to enter into a certain differentiation pathway depends in many cases on signals from neighbouring cells. The ability of cells to engage in short-range intercellular communication permits the coordination of cell actions necessary in many developmental processes. Overexpression of genes from the DEVIL/ROTUNDIFOLIA (DVL/ROT) family results in severe developmental alterations, but very little is known about their mechanism of action. This work presents evidence that suggests a role for these genes in local signalling, specifically in the coordination of socket cell recruitment and differentiation. Overexpression of different DVL genes results in protuberances at the base of the trichomes surrounded by several rows of elongated epidermal cells, morphologically similar to socket cells. Localized overexpression of DVL4 in trichomes and socket cells during early developmental stages activates expression of socket cell markers in additional cells, farther away from the trichome. The same phenomenon is observed in an activation tagged line of DVL1, which also shows an increase in the number of socket cells in contact with the trichome. The roles of individual DVL genes have been difficult to discover since their overexpression phenotypes are quite similar. In gl1 leaves that lack trichomes and socket cells DVL1 expression shows a 69% reduction, suggesting that this gene could be involved in the coordination of socket cell development in wild-type plants.

La termografía como nueva herramienta de evaluación en baloncesto. Estudio piloto realizado a un jugador profesional de la ACB / No disponible

INTRODUCCIÓN: La termografía infrarroja (IFT) es una herramienta de análisis que no emite irradiación y no es invasiva por lo que es adecuada para el estudio de las funciones fisiológicas relacionadas con el control de temperatura de la piel. OBJETIVOS: Establecer el comportamiento termográfico de un jugador de baloncesto. MATERIAL Y MÉTODOS: En el estudio ha participado un jugador profesional de la ACB. Tras respetar el periodo de aclimatación y cumplir el protocolo de la International Academy of Clinical Thermology (IACT) se han tomado 4 imágenes termográficas, dos de la visión anterior (miembro superior e inferior) y dos de la visión posterior (miembro superior e inferior). RESULTADOS: Se han encontrado diferencias de más de 0.5ºC entre áreas simétricas del cuerpo. CONCLUSIONES: La termografía es una herramienta válida, rápida y segura que nos permite cuantificar el estado térmico del sujeto y controlar su evolución (AU)

INTRODUCTION: Infrared thermography (IFT) is ananalysis tool that emits no radiation and is non-invasive, making it suitable for the study of physiological functions related to the control of skin temperature. OBJECTIVES: To establish the thermographic behaviour of a professional basketball player. MATERIALS AND METHODS: The study involved a professional player in the ACB. Four thermal images were taken after the acclimation period to respect the protocol of the International Academy of Clinical Thermology (IACT) (two anterior views (upper and lower limbs) and two posterior views (upper and lower limbs). RESULTS: There were differences of more than 0.5 º C between symmetrical areas of the body. CONCLUSIONS: Thermography is a valid, fast and safe too land allows the thermal state of the subject to be quantified and its evolution monitored (AU)

Bicarbonate ingestion has no ergogenic effect on consecutive all out sprint tests in BMX elite cyclists.

The aim of the present study was to examine the effect of sodium bicarbonate ingestion on consecutive "all out" sprint tests, analyzing the acid-base status and its influence on performance and perceived effort. Ten elite bicycle motocross (BMX) riders (20.7 ± 1.4 years, training experience 8-12 years) participated in this study which consisted of two trials. Each trial consisted of three consecutive Wingate tests (WTs) separated by 15 min recovery. Ninety minutes prior to exercise subjects ingested either NaHCO(3) (-) (0.3 g kg(-1) body weight) or placebo. Blood samples were collected for the assessment of blood acid-base status: bicarbonate concentration ([HCO(3) (-)]), pH, base excess (BE) and blood lactate concentration ([La(-)]). Performance variables of peak power (PP), mean power (MP), time to peak power and fatigue index were calculated for each sprint. Significant differences (p < 0.05) were observed in acid-base variables [pH before WT1: 7.47 ± 0.05 vs. 7.41 ± 0.03; [HCO(3) (-)] before WT1: 29.08 ± 2.27 vs. 22.85 ± 0.24 mmol L(-1) (bicarbonate vs. placebo conditions, respectively)], but there were not significant differences in performance variables between trials [PP WT1: 1,610 ± 373 vs. 1,599 ± 370 W; PP WT2: 1,548 ± 460 vs. 1,570 ± 428 W; PP WT3: 1,463 ± 361 vs. 1,519 ± 364 W. MP WT1: 809 ± 113 vs. 812 ± 108 W; MP WT2: 799 ± 135 vs. 799 ± 124 W; MP WT3: 762 ± 165 vs. 782 ± 118 W (bicarbonate vs. placebo conditions, respectively)]. Rating of perceived effort (RPE) was not influenced nor ratings of perceived readiness. Sodium bicarbonate ingestion modified significantly the blood acid-base balance, although the induced alkalosis did not improve the Wingate test performance, RPE and perceived readiness across three consecutive WTs in elite BMX cyclists.

Influence of opposition on ball velocity in the handball jump throw.

The purpose of the present study was to investigate the influence of different degrees of opposition on ball velocity in the jump throw in elite, amateur and adolescent team handball players. Thus, one hundred and nineteen elite, amateur and under 18 team handball players performed jump throws under three different conditions: 1) without opposition, 2) with the opposition of the goalkeeper and 3) with the opposition of the goalkeeper and a defensive player. The degree of opposition was found to have a negative effect on ball velocity in all three groups (p < 0.001). Furthermore, the level of competition had a positive effect on ball velocity (p < 0.001). However, no interaction was found between the level of competition and the degree of opposition on ball velocity (p = 0.178). The findings of this study indicate that an increase of external stimuli probably influences throwing kinematics and thereby maximal ball velocity. However, experience does not seem to be a factor that can reduce the influence of these external stimuli. Key pointsThe degree of opposition had a negative effect upon ball throwing velocity in elite, amateur and adolescent handball players in the jump throw.It indicated that an increase of external stimuli influences the execution of throwing.Experience does not seem to be a factor that can reduce the influence of these external stimuli.

Lack of α-xylosidase activity in Arabidopsis alters xyloglucan composition and results in growth defects.

Xyloglucan is the main hemicellulose in the primary cell walls of most seed plants and is thought to play a role in regulating the separation of cellulose microfibrils during growth. Xylose side chains block the degradation of the backbone, and α-xylosidase activity is necessary to remove them. Two Arabidopsis (Arabidopsis thaliana) mutant lines with insertions in the α-xylosidase gene AtXYL1 were characterized in this work. Both lines showed a reduction to undetectable levels of α-xylosidase activity against xyloglucan oligosaccharides. This reduction resulted in the accumulation of XXXG and XXLG in the liquid growth medium of Atxyl1 seedlings. The presence of XXLG suggests that it is a poor substrate for xyloglucan ß-galactosidase. In addition, the polymeric xyloglucan of Atxyl1 lines was found to be enriched in XXLG subunits, with a concomitant decrease in XXFG and XLFG. This change can be explained by extensive exoglycosidase activity at the nonreducing ends of xyloglucan chains. These enzymes could thus have a larger role than previously thought in the metabolism of xyloglucan. Finally, Atxyl1 lines showed a reduced ability to control the anisotropic growth pattern of different organs, pointing to the importance of xyloglucan in this process. The promoter of AtXYL1 was shown to direct expression to many different organs and cell types undergoing cell wall modifications, including trichomes, vasculature, stomata, and elongating anther filaments.

Potential role for purple acid phosphatase in the dephosphorylation of wall proteins in tobacco cells.

It is not yet known whether dephosphorylation of proteins catalyzed by phosphatases occurs in the apoplastic space. In this study, we found that tobacco (Nicotiana tabacum) purple acid phosphatase could dephosphorylate the phosphoryl residues of three apoplastic proteins, two of which were identified as alpha-xylosidase and beta-glucosidase. The dephosphorylation and phosphorylation of recombinant alpha-xylosidase resulted in a decrease and an increase in its activity, respectively, when xyloglucan heptasaccharide was used as a substrate. Attempted overexpression of the tobacco purple acid phosphatase NtPAP12 in tobacco cells not only decreased the activity levels of the glycosidases but also increased levels of xyloglucan oligosaccharides and cello-oligosaccharides in the apoplast during the exponential phase. We suggest that purple acid phosphatase controls the activity of alpha-xylosidase and beta-glucosidase, which are responsible for the degradation of xyloglucan oligosaccharides and cello-oligosaccharides in the cell walls.

Control biológico del sobreentrenamiento en un mesociclo precompetitivo en triatletas de élite: un estudio piloto / Biological control of training during the precompetitive period in elite triathletes: A pilot study

El objetivo de este trabajo fue controlar la evolución de parámetros bioquímicos comúnmente relacionados con el sobre entrenamiento en cinco semanas previas a una competición de importancia en triatletas de élite. Durante cinco semanas se controló el entrenamiento de cinco triatletas masculinos de élite (VO2max 77,6±5,1 mL•min-1•kg-1). En este periodo, se fijó una estructura de los microciclos con un día de carga seguido de otro de recuperación. En los días posteriores a la carga y la recuperación se obtuvieron muestras sanguíneas para la determinación de la concentración de urea (U), creatin kinasa (CK), testosterona total (T) y cortisol total (C). El entrenamiento se controló obteniendo datos de las distancias recorridas en natación, ciclismo y carrera. El volumen total de entrenamiento varió entre un máximo de 78,1 km en el microciclo 3 y 40,8 km en el microciclo 4. Tanto U como CK experimentaron un aumento significativo (comparado con valores de referencia al inicio de la temporada) durante la carga en cuatro de las cinco semanas de estudio. Además, tras la recuperación estos parámetros no volvieron a los valores de referencia de dos semanas para la CK y tres semanas para la U, sin embargo, ninguno de los triatletas experimentó otros síntomas de sobre entrenamiento tales como falta de sueño. Por otro lado, la relación T/C no descendió más del 30% respecto a la analítica de referencia en ninguno de los microciclos. Así, concluimos que los triatletas de élite, ante un mesociclo controlado y bajo supervisión bioquímica periódica del entrenamiento no parecen percibir ni experimentar síntomas de sobre entrenamiento durante las semanas previas a una competición (AU)

The aim of this study was to control the evolution of biochemical parameters commonly associated with over training in five weeks before a major competition in elite triathletes. During five weeks, training was controlled in five elite male elite triathletes (VO2max 77,6±5,1 mL•min•kg-1).In this period, microcyles structure was fixed with one day of high load followed by another of recovery. The days after the loading and recovery blood samples were obtained to determine the concentration of urea (U), creatine kinase(CK), total testosterone (T) and total cortisol (C). Training volume was obtained from distances covered in swimming, cycling and running. Total volume training changed from a maximum of 78,1 km duing microcycle 3 and 40,8 km during microcycle 4. Both, U and CK experienced a significant increase (compared with reference values at the start of the season) during loading in four of the five weeks of study. Moreover, following the recovery, these parameters did not returned to the baseline levels in two weeks for the CK and three weeks for the U. However, triathletes did not report any overtraining symptom as lack of sleep. Furthermore, the relación T/C did not fall more than 30% of the analytical reference. Thus, we concluded that the elite triathletes do not experience symptoms of overtraining during the weeks before a competition, at least when it is assessed by biochemical parameters (AU)

Analysis of men´s and women´s basketball fast-breaks

In the present study, the way basketball fast breaks are executed was analysed, while determining how the bestresults are obtained and studying the differences between the men’s and women’s game. Utilizing observational methodology, atotal of 294 fast breaks were analysed from 30 games played at the 2008 Olympic Games in Beijing. Eighteen of the games werehigh-level men’s games and 12 were high-level women’s games. Statistically significant differences were observed between themen’s and the women’s game in the following aspects with regard to fast breaks: (1) duration, (2) completion area, and (3) shotopposition. For men, some dependence relationships were found between the fast break result and the following variables:duration, completion area, and opposition to its completion. For women, the results revealed a weak association between the fastbreak result and the opposition to its completion(AU)

Recent proliferation and translocation of pollen group 1 allergen genes in the maize genome.

The dominant allergenic components of grass pollen are known by immunologists as group 1 allergens. These constitute a set of closely related proteins from the beta-expansin family and have been shown to have cell wall-loosening activity. Group 1 allergens may facilitate the penetration of pollen tubes through the grass stigma and style. In maize (Zea mays), group 1 allergens are divided into two classes, A and B. We have identified 15 genes encoding group 1 allergens in maize, 11 genes in class A and four genes in class B, as well as seven pseudogenes. The genes in class A can be divided by sequence relatedness into two complexes, whereas the genes in class B constitute a single complex. Most of the genes identified are represented in pollen-specific expressed sequence tag libraries and are under purifying selection, despite the presence of multiple copies that are nearly identical. Group 1 allergen genes are clustered in at least six different genomic locations. The single class B location and one of the class A locations show synteny with the rice (Oryza sativa) regions where orthologous genes are found. Both classes are expressed at high levels in mature pollen but at low levels in immature flowers. The set of genes encoding maize group 1 allergens is more complex than originally anticipated. If this situation is common in grasses, it may account for the large number of protein variants, or group 1 isoallergens, identified previously in turf grass pollen by immunologists.

Genome histories clarify evolution of the expansin superfamily: new insights from the poplar genome and pine ESTs.

Expansins comprise a superfamily of plant cell wall-loosening proteins that has been divided into four distinct families, EXPA, EXPB, EXLA and EXLB. In a recent analysis of Arabidopsis thaliana and Oryza sativa expansins, we proposed a further subdivision of the families into 17 clades, representing independent lineages in the last common ancestor of monocots and eudicots. This division was based on both traditional sequence-based phylogenetic trees and on position-based trees, in which genomic locations and dated segmental duplications were used to reconstruct gene phylogeny. In this article we review recent work concerning the patterns of expansin evolution in angiosperms and include additional insights gained from the genome of a second eudicot species, Populus trichocarpa, which includes at least 36 expansin genes. All of the previously proposed monocot-eudicot orthologous groups, but no additional ones, are represented in this species. The results also confirm that all of these clades are truly independent lineages. Furthermore, we have used position-based phylogeny to clarify the history of clades EXPA-II and EXPA-IV. Most of the growth of the expansin superfamily in the poplar lineage is likely due to a recent polyploidy event. Finally, some monocot-eudicot clades are shown to have diverged before the separation of the angiosperm and gymnosperm lineages.