Unraveling Rice Tolerance Mechanisms Against Schizotetranychus oryzae Mite Infestation.

Rice is the staple food for over half of the world's population. Infestation of Schizotetranychus oryzae (Acari: Tetranychidae) causes great losses in rice productivity. To search for rice genotypes that could better tolerate S. oryzae infestation, we evaluated morphological and production parameters in Brazilian cultivars, and identified two cultivars with contrasting responses. Leaf damage during infestation was similar for all cultivars. However, infestation in Puitá INTA-CL resulted in reduction in the number of seeds per plant, percentage of full seeds, weight of 1,000 seeds, and seed length, whereas infestation in IRGA 423 increased weight of 1,000 seeds and seed length. Reduction in seed weight per plant caused by infestation was clearly higher in Puitá INTA-CL (62%) compared to IRGA 423 (no reduction detected), thus Puitá INTA-CL was established as susceptible, and IRGA 423 as tolerant to S. oryzae infestation. Photosynthetic parameters were less affected by infestation in IRGA 423 than in Puitá INTA-CL, evidencing higher efficiency of energy absorption and use. S. oryzae infestation also caused accumulation of H2O2, decreased cell membrane integrity (indicative of cell death), and accelerated senescence in leaves of Puitá INTA-CL, while leaves of IRGA 423 presented higher levels of total phenolics compounds. We performed proteomics analysis of Puitá INTA-CL and IRGA 423 leaves after 7 days of infestation, and identified 60 differentially abundant proteins (28 more abundant in leaves of Puitá INTA-CL and 32 in IRGA 423). Proteins related to plant defense, such as jasmonate synthesis, and related to other mechanisms of tolerance such as oxidative stress, photosynthesis, and DNA structure maintenance, together with energy production and general metabolic processes, were more abundant in IRGA 423. We also detected higher levels of silicon (as amorphous silica cells) in leaves of infested IRGA 423 plants compared to Puitá INTA-CL, an element previously linked to plant defense, indicating that it could be involved in tolerance mechanisms. Taken together, our data show that IRGA 423 presents tolerance to S. oryzae infestation, and that multiple mechanisms might be employed by this cultivar. These findings could be used in biotechnological approaches aiming to increase rice tolerance to mite infestation.

Insights from Proteomic Studies into Plant Somatic Embryogenesis.

Somatic embryogenesis is a biotechnological approach mainly used for the clonal propagation of different plants worldwide. In somatic embryogenesis, embryos arise from somatic cells under appropriate culture conditions. This plasticity in plants is a demonstration of true cellular totipotency and is the best approach among the genetic transformation protocols used for plant regeneration. Despite the importance of somatic embryogenesis, knowledge regarding the control of the somatic embryogenesis process is limited. Therefore, the elucidation of both the biochemical and molecular processes is important for understanding the mechanisms by which a single somatic cell becomes a whole plant. Modern proteomic techniques rely on an alternative method for the identification and quantification of proteins with different abundances in embryogenic cell cultures or somatic embryos and enable the identification of specific proteins related to somatic embryogenesis development. This review focuses on somatic embryogenesis studies that use gel-free shotgun proteomic analyses to categorize proteins that could enhance our understanding of particular aspects of the somatic embryogenesis process and identify possible targets for future studies.

Somatic Embryogenesis in Peach-Palm (Bactris gasipaes) Using Different Explant Sources.

Peach palm (Bactris gasipaes Kunth) is a member of the family Arecaceae and is a multipurpose but underutilized species. Nowadays, fruit production for subsistence and local markets, and heart-of-palm production for local, national, and international markets are the most important uses of this plant. Conventional breeding programs in peach palm are long-term efforts due to the prolonged generation time, large plant size, difficulties with controlled pollination and other factors. Although it is a caespitose palm, its propagation is currently based on seeds, as off-shoots are difficult to root. Hence, tissue culture techniques are considered to be the most likely strategy for efficient clonal plantlet regeneration of this species. Among various techniques, somatic embryogenesis offers the advantages of potential automated large-scale production and putative genetic stability of the regenerated plantlets. The induction of somatic embryogenesis in peach palm can be achieved by using different explant sources including zygotic embryos, immature inflorescences and thin cell layers from the young leaves and shoot meristems. The choice of a particular explant depends on whether clonal propagation is desired or not, as well as on the plant conditions and availability of explants. Protocols to induce and express somatic embryogenesis from different peach palm explants, up to acclimatization of plantlets, are described in this chapter.

Label-Free Quantitative Proteomics of Embryogenic and Non-Embryogenic Callus during Sugarcane Somatic Embryogenesis.

The development of somatic cells in to embryogenic cells occurs in several stages and ends in somatic embryo formation, though most of these biochemical and molecular changes have yet to be elucidated. Somatic embryogenesis coupled with genetic transformation could be a biotechnological tool to improve potential crop yields potential in sugarcane cultivars. The objective of this study was to observe somatic embryo development and to identify differentially expressed proteins in embryogenic (E) and non-embryogenic (NE) callus during maturation treatment. E and NE callus were cultured on maturation culture medium supplemented with different concentrations (0.0, 0.75, 1.5 and 2.0 g L(-1)) of activated charcoal (AC). Somatic embryo formation and differential protein expression were evaluated at days 0 and 21 using shotgun proteomic analyses. Treatment with 1.5 g L(-1) AC resulted in higher somatic embryo maturation rates (158 somatic embryos in 14 days) in E callus but has no effect in NE callus. A total of 752 co-expressed proteins were identified through the SUCEST (The Sugarcane EST Project), including many housekeeping proteins. E callus showed 65 exclusive proteins on day 0, including dehydrogenase, desiccation-related protein, callose synthase 1 and nitric oxide synthase. After 21 days on maturation treatment, 14 exclusive proteins were identified in E callus, including catalase and secreted protein. NE callus showed 23 exclusive proteins on day 0 and 10 exclusive proteins after 21 days on maturation treatment, including many proteins related to protein degradation. The induction of maturation leads to somatic embryo development, which likely depends on the expression of specific proteins throughout the process, as seen in E callus under maturation treatment. On the other hand, some exclusive proteins can also specifically prevent of somatic embryos development, as seen in the NE callus.

Comparative proteomic analysis of somatic embryo maturation in Carica papaya L.

BACKGROUND: Somatic embryogenesis is a complex process regulated by numerous factors. The identification of proteins that are differentially expressed during plant development could result in the development of molecular markers of plant metabolism and provide information contributing to the monitoring and understanding of different biological responses. In addition, the identification of molecular markers could lead to the optimization of protocols allowing the use of biotechnology for papaya propagation and reproduction. This work aimed to investigate the effects of polyethylene glycol (PEG) on somatic embryo development and the protein expression profile during somatic embryo maturation in papaya (Carica papaya L.). RESULTS: The maturation treatment supplemented with 6% PEG (PEG6) resulted in the greatest number of somatic embryos and induced differential protein expression compared with cultures grown under the control treatment. Among 135 spots selected for MS/MS analysis, 76 spots were successfully identified, 38 of which were common to both treatments, while 14 spots were unique to the control treatment, and 24 spots were unique to the PEG6 treatment. The identified proteins were assigned to seven categories or were unclassified. The most representative class of proteins observed in the control treatment was associated with the stress response (25.8%), while those under PEG6 treatment were carbohydrate and energy metabolism (18.4%) and the stress response (18.4%). CONCLUSIONS: The differential expression of three proteins (enolase, esterase and ADH3) induced by PEG6 treatment could play an important role in maturation, and these proteins could be characterized as candidate biomarkers of somatic embryogenesis in papaya.

Survival and ultrastructural features of peach palm (Bactris gasipaes, Kunth) somatic embryos submitted to cryopreservation through vitrification.

Bactris gasipaes (Arecaceae), also known as peach palm, was domesticated by Amazonian Indians and is cultivated for its fruit and heart-of-palm, a vegetable grown in the tree's inner core. Currently, the conservation of this species relies on in situ conditions and field gene banks. Complementary conservation strategies, such as those based on in vitro techniques, are indicated in such cases. To establish an appropriate cryopreservation protocol, this study aimed to evaluate the ultrastructural features of B. gasipaes embryogenic cultures submitted to vitrification and subsequent cryogenic temperatures. Accordingly, somatic embryo clusters were submitted to Plant Vitrification Solution 3 (PVS3). In general, cells submitted to PVS3 had viable cell characteristics associated with apparently many mitochondria, prominent nucleus, and preserved cell walls. Cells not incubated in PVS3 did not survive after the cryogenic process in liquid nitrogen. The best incubation time for the vitrification technique was 240 min, resulting in a survival rate of 37 %. In these cases, several features were indicative of quite active cell metabolism, including intact nuclei and preserved cell walls, an apparently many of mitochondria and lipid bodies, and the presence of many starch granules and condensed chromatin. Moreover, ultrastructure analysis revealed that overall cellular structures had been preserved after cryogenic treatment, thus validating the use of vitrification in conjunction with cryopreservation of peach palm elite genotypes, as well as wild genotypes, which carry a rich pool of genes that must be conserved.