Dynamic changes in calcium signals during root gravitropism.

Gravitropism is a vital mechanism through which plants adapt to their environment. Previous studies indicated that Ca2+ may play an important role in plant gravitropism. However, our understanding of the calcium signals in root gravitropism is still largely limited. Using a vertical stage confocal and transgenic Arabidopsis R-GECO1, our data showed that gravity stimulation enhances the occurrence of calcium spikes and increases the Ca2+ concentration in the lower side of the root cap. Furthermore, a close correlation was observed in the asymmetry of calcium signals with the inclination angles at which the roots were oriented. The frequency of calcium spikes on the lower side of 90°-rotated root decreases rapidly over time, whereas the asymmetric distribution of auxin readily strengthens for up to 3 h, indicating that the calcium spikes, promoted by gravity stimulation, may precede auxin as one of the early signals. In addition, the root gravitropism of starchless mutants is severely impaired. Correspondingly, no significant increase in calcium spike occurrence was observed in the root caps of these mutants within 15 min following a 90° rotation, indicating the involvement of starch grains in the formation of calcium spikes. However, between 30 and 45 min after a 90° rotation, asymmetric calcium spikes were indeed observed in the root of starchless mutants, suggesting that starch grains are not indispensable for the formation of calcium spikes. Besides, co-localization analysis suggests that the ER may function as calcium stores during the occurrence of calcium spikes. These findings provide further insights into plant gravitropism.

Anatomy and Comparative Transcriptome Reveal the Mechanism of Male Sterility in Salvia miltiorrhiza.

Salvia miltiorrhiza Bunge is an important traditional herb. Salvia miltiorrhiza is distributed in the Sichuan province of China (here called SC). Under natural conditions, it does not bear seeds and its sterility mechanism is still unclear. Through artificial cross, there was defective pistil and partial pollen abortion in these plants. Electron microscopy results showed that the defective pollen wall was caused by delayed degradation of the tapetum. Due to the lack of starch and organelle, the abortive pollen grains showed shrinkage. RNA-seq was performed to explore the molecular mechanisms of pollen abortion. KEGG enrichment analysis suggested that the pathways of phytohormone, starch, lipid, pectin, and phenylpropanoid affected the fertility of S. miltiorrhiza. Moreover, some differentially expressed genes involved in starch synthesis and plant hormone signaling were identified. These results contribute to the molecular mechanism of pollen sterility and provide a more theoretical foundation for molecular-assisted breeding.

Plant foods consumed at the Neolithic site of Qujialing (ca. 5800-4200 BP) in Jianghan Plain of the middle catchment of Yangtze River, China.

The site of Qujialing experienced a long, sustained process of the development of Neolithic culture in the Jianghan Plain, with a period of some1600 years. Our previous studies based on macrofossil remains and phytoliths revealed that rice (Oryza sativa) from Qujialing was already domesticated, and millet (Setaria italica and Panicum miliaceum) had also been spread into the site since the Youziling Culture period (5800-5100 BP). Nevertheless, no direct evidence has been provided regarding the daily consumed plant foods, especially plant foods obtained by gathering, throughout the site occupation. This paper thus examines pottery sherds (n=41) associated with culinary practices from Qujialing with starch grain analysis. Apart from starch grains from rice and millet, the results indicate that job's tears (Coix lacryma-jobi), lotus roots (Nelumbo nucifera), tubers possibly from Chinese yam (Dioscorea panthainca), acorns (Quercus sp.), and beans (Vigna sp. or/and Vicia sp.) were consumed by the ancient Qujialing people, within job's tears and lotus roots were not discovered before in the macrofossil remains and phytoliths. Combining the starch data and multiple lines of evidence from macrofossil remains and phytoliths, it is suggested that rice was among the most frequently consumed plant foods since the first occupation phase at Qujialing, while acorns could have been gradually replaced by other agricultural products (i.e., rice) and became less important food ingredients, especially when agriculture was more developed in the last occupation phase at Qujialing. These novel findings not only complement our previous research by providing the first line of evidence of paleodiet in the Jianghan Plain from the perspective of starch grain analysis but also delivers a better understanding of the characterized dietary trends and agricultural development in the research region.

Three Diverse Granule Preparation Methods for Proteomic Analysis of Mature Rice (Oryza sativa L.) Starch Grain.

Starch is the primary form of reserve carbohydrate storage in plants. Rice (Oryza sativa L.) is a monocot whose reserve starch is organized into compounded structures within the amyloplast, rather than a simple starch grain (SG). The mechanism governing the assembly of the compound SG from polyhedral granules in apposition, however, remains unknown. To further characterize the proteome associated with these compounded structures, three distinct methods of starch granule preparation (dispersion, microsieve, and flotation) were performed. Phase separation of peptides (aqueous trypsin-shaving and isopropanol solubilization of residual peptides) isolated starch granule-associated proteins (SGAPs) from the distal proteome of the amyloplast and the proximal 'amylome' (the amyloplastic proteome), respectively. The term 'distal proteome' refers to SGAPs loosely tethered to the amyloplast, ones that can be rapidly proteolyzed, while proximal SGAPs are those found closer to the remnant amyloplast membrane fragments, perhaps embedded therein-ones that need isopropanol solvent to be removed from the mature organelle surface. These two rice starch-associated peptide samples were analyzed using nano-liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). Known and novel proteins, as well as septum-like structure (SLS) proteins, in the mature rice SG were found. Data mining and gene ontology software were used to categorize these putative plastoskeletal components as a variety of structural elements, including actins, tubulins, tubulin-like proteins, and cementitious elements such as reticulata related-like (RER) proteins, tegument proteins, and lectins. Delineating the plastoskeletal proteome begins by understanding how each starch granule isolation procedure affects observed cytoplasmic and plastid proteins. The three methods described herein show how the technique used to isolate SGs differentially impacts the subsequent proteomic analysis and results obtained. It can thus be concluded that future investigations must make judicious decisions regarding the methodology used in extracting proteomic information from the compound starch granules being assessed, since different methods are shown to yield contrasting results herein. Data are available via ProteomeXchange with identifier PXD032314.

ENLARGED STARCH GRAIN1 affects amyloplast development and starch biosynthesis in rice endosperm.

Cereal crops accumulate large amounts of starch which is synthesized and stored in amyloplasts in the form of starch grains (SGs). Despite significant progress in deciphering starch biosynthesis, our understanding of amyloplast development in rice (Oryza sativa) endosperm remains largely unknown. Here, we report a novel rice floury mutant named enlarged starch grain1 (esg1). The mutant has decreased starch content, altered starch physicochemical properties, slower grain-filling rate and reduced 1000-grain weight. A distinctive feature in esg1 endosperm is that SGs are much larger, mainly due to an increased number of starch granules per SG. Spherical and loosely assembled granules, together with those weakly stained SGs may account for decreased starch content in esg1. Map-based cloning revealed that ESG1 encodes a putative permease subunit of a bacterial-type ABC (ATP-binding cassette) lipid transporter. ESG1 is constitutively expressed in various tissues. It encodes a protein localized to the chloroplast and amyloplast membranes. Mutation of ESG1 causes defective galactolipid synthesis. The overall study indicates that ESG1 is a newly identified protein affecting SG development and subsequent starch biosynthesis, which provides novel insights into amyloplast development in rice.

Occurrence of internal browning in tuberous roots of sweetpotato and its related starch biosynthesis.

Although sweetpotato is an important crop worldwide, there has been almost no research on the occurrence of internal browning (IB) to date. In this study, we clarified the mechanism of occurrence of the disorder by using two types of cultivars with different IB susceptibility. In cells around the secondary vascular tissue, large size of starch grains accumulated in IB-susceptible cultivar compared with resistant one. Histochemical observation performed on cells around the secondary vascular tissues showed the presence of high levels of polyphenol oxidase activity, chlorogenic acid, and hydrogen peroxide in cells from the IB-affected regions in IB-susceptible cultivar. Likewise, high levels of starch content, hydrogen peroxide concentration, and polyphenol content were detected in the affected regions of IB-susceptible cultivar. In IB-susceptible cultivar, both the transcript levels of gens related starch and polyphenol biosynthesis were higher at an early stage of root maturation, while the levels in resistant cultivar were low at this stage and thereafter increased relatively more moderately. These observations suggest that the occurrence of IB disorder in sweetpotato largely depends on the morphology and timing of accumulated starch grain in cells around the secondary vascular tissues.

Effects of changes in micro-weather conditions on structural features, total protein and carbohydrate content in leaves of the Atlantic rain forest tree golden trumpet (Tabebuia chrysotricha) / Efeito de alterações nas condições micro-climáticas sobre características estruturais, e proteína e carboidratos histoquimicamente marcados, de folhas da árvore da floresta Atlântica ipê amarelo

Abstract Golden trumpet, Tabebuia chrysotricha, is a native tree from the Brazilian Atlantic rain forest, with a broad latitudinal distribution. In this study, we investigated the potential effects of short-term changes in micro-weather conditions on structural features, and total protein and carbohydrate content of golden trumpet leaves, using structural and histochemical approaches. Leaves were harvested in four different micro-weather conditions: 1. Afternoon, after a hot, sunny day; 2. at dawn, after a previously hot, sunny day; 3. at noon, of a hot, sunny day; and 4. at noon, of a cold, cloudy day. Leaflets exposed to low light irradiance showed flattened chloroplasts, uniformly distributed within the cells, throughout the palisade parenchyma. Conversely, leaflets exposed to high light irradiance presented flattened and rounded chloroplasts, in the upper and lower palisade parenchyma cells, respectively. The strongest protein staining was found for leaves harvested at the coldest period, whereas the weakest protein staining was found for leaves harvested after a hot, sunny day. The largest and most numerous starch grains were found for leaves harvested in the afternoon, after a hot, sunny day. Conversely, the smallest and less numerous starch grains were found for leaves harvested at dawn. Analysis of the data reported herein suggests that the leaflet responses to transient changes in micro-weather conditions are likely to contribute to the golden trumpet successful establishment in the broad latitudinal distribution in which the species is found.

Resumo Ipê amarelo é uma árvore nativa da floresta Atlântica brasileira, encontrada em uma ampla distribuição latitudinal. Neste estudo, nós investigamos os efeitos potenciais de alterações de curto prazo nas condições micro-climáticas sobre características estruturais, proteína e carboidratos histoquimicamente marcados, de folhas de ipê amarelo, usando estratégias de análise estrutural e histoquímicas. As folhas foram marcadas em quatro condições microclimáticas distintas: 1. Tarde, após um dia quente e ensolarado; 2. Amanhecer, após um dia quente e ensolarado; 3. Ao meio-dia, de um dia quente e ensolarado; e 4. Ao meio-dia, de um dia frio e nublado. Folíolos expostos à baixa irradiância luminosa apresentaram cloroplastos achatados, uniformemente distribuídos no interior das células, por todo o parênquima paliçádico, enquanto que folíolos expostos à alta irradiância apresentaram cloroplastos achatados e arredondados, nas células superiores e inferiores do parênquima paliçádico, respectivamente. A marcação mais intensa para proteína foi observada para folhas coletadas no momento mais frio de coleta, enquanto que a marcação mais fraca foi observada para folhas coletadas após um dia quente e ensolarado. Os grãos de amido maiores e mais numerosos foram observados em folhas coletadas durante a tarde de dia quente e ensolarado, enquanto que os menores e menos numerosos grãos de amido foram observados em folhas coletadas ao amanhecer.

Plant foods and the dietary ecology of Neanderthals and early modern humans.

One of the most important challenges in anthropology is understanding the disappearance of Neanderthals. Previous research suggests that Neanderthals had a narrower diet than early modern humans, in part because they lacked various social and technological advances that lead to greater dietary variety, such as a sexual division of labor and the use of complex projectile weapons. The wider diet of early modern humans would have provided more calories and nutrients, increasing fertility, decreasing mortality and supporting large population sizes, allowing them to out-compete Neanderthals. However, this model for Neanderthal dietary behavior is based on analysis of animal remains, stable isotopes, and other methods that provide evidence only of animal food in the diet. This model does not take into account the potential role of plant food. Here we present results from the first broad comparison of plant foods in the diets of Neanderthals and early modern humans from several populations in Europe, the Near East, and Africa. Our data comes from the analysis of plant microremains (starch grains and phytoliths) in dental calculus and on stone tools. Our results suggest that both species consumed a similarly wide array of plant foods, including foods that are often considered low-ranked, like underground storage organs and grass seeds. Plants were consumed across the entire range of individuals and sites we examined, and none of the expected predictors of variation (species, geographic region, or associated stone tool technology) had a strong influence on the number of plant species consumed. Our data suggest that Neanderthal dietary ecology was more complex than previously thought. This implies that the relationship between Neanderthal technology, social behavior, and food acquisition strategies must be better explored.