Giseli Buffon

Ubiquitination pathway as a target to develop abiotic stress tolerance in rice

Abiotic stresses may result in significant losses in rice grain productivity. Protein regulation by the ubiquitin/proteasome system has been studied as a target mechanism to optimize adaptation and survival strategies of plants to different environmental stresses. This article aimed at highlighting recent discoveries about the roles ubiquitination may play in the exposure of rice plants to different abiotic stresses, enabling the development of modified plants tolerant to stress. Responses provided by the ubiquitination process include the regulation of the stomatal opening, phytohormones levels, protein stabilization, cell membrane integrity, meristematic cell maintenance, as well as the regulation of reactive oxygen species and heavy metals levels. It is noticeable that ubiquitination is a potential means for developing abiotic stress tolerant plants, being an excellent alternative to rice (and other cultures) improvement programs.

Alterations in rice, corn and wheat plants infested by phytophagous mite

Phytophagous mites (Acari) are agricultural pests that cause productivity and economic losses. Mite infestation is stressful for plants, hindering the development and harming photosynthetic structures and storage organs. In order to combat such damage, plants utilize molecular and physiological modifications, as well as the production of mite-inhibitory compounds. In this review, we focus on the main phytophagous mites that infest the most commercially important cereals – rice (Oryza sativa L.), corn (Zea mays L.) and wheat (Triticum aestivum L.) – summarizing the responses of the plants – physiological and molecular alterations – to mite infestation.

Physiological and Molecular Alterations Promoted by Schizotetranychus oryzae Mite Infestation in Rice Leaves

Infestation of phytophagous mite Schizotetranychus oryzae in rice causes critical yield losses. To better understand this interaction, we employed Multidimensional Protein Identification Technology (MudPIT) approach to identify differentially expressed proteins. We detected 18 and 872 unique proteins in control and infested leaves, respectively, along with 32 proteins more abundant in control leaves. S. oryzae infestation caused decreased abundance of proteins related to photosynthesis (mostly photosystem II-related), carbon assimilation and energy production, chloroplast detoxification, defense, and fatty acid and gibberellin synthesis. On the contrary, infestation caused increased abundance of proteins involved in protein modification and degradation, gene expression at the translation level, protein partitioning to different organelles, lipid metabolism, actin cytoskeleton remodeling, and synthesis of jasmonate, amino acid, and molecular chaperones. Our results also suggest that S. oryzae infestation promotes cell-wall remodeling and interferes with ethylene biosynthesis in rice leaves. Proteomic data were positively correlated with enzymatic assays and RT-qPCR analysis. Our findings describe the protein expression patterns of infested rice leaves and suggest that the acceptor side of PSII is probably the major damaged target in the photosynthetic apparatus. These data will be useful in future biotechnological approaches aiming to induce phytophagous mite resistance in rice.

Checkmite!? Is the Resistance to Phytophagous Mites on Short and Stocky Wild Oryza Species?

Graduate Program in Biotechnology, University of Taquari Valley, Univates, Lajeado, Brazil, 2 Biological Sciences and Health Center, University of Taquari Valley, Univates, Lajeado, Brazil, Graduate Program in Biotechnology, University of Caxias do Sul, Caxias do Sul, Brazil, Graduate Program in Agrobiology, Federal University of Santa Maria, Santa Maria, Brazil, Graduate Program in Cell and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil

High infestation levels of Schizotetranychus oryzae severely affects rice metabolism

High levels of Schizotetranychus oryzae phytophagous mite infestation on rice leaves can severely affect productivity. Physiological characterization showed that S. oryzae promotes a decrease in chlorophyll concentration and the establishment of a senescence process in rice leaves. Late-infested leaves also present high levels of superoxide radical and hydrogen peroxide accumulation, along with high levels of membrane integrity loss, which is indicative of cell death. To better understand the rice molecular responses to high levels of mite infestation, we employed the Multidimensional Protein Identification Technology (MudPIT) approach to identify differentially expressed proteins. We identified 83 and 88 proteins uniquely present in control and late-infested leaves, respectively, along with 11 and one proteins more abundant in control and late-infested leaves, respectively. S. oryzae infestation induces a decreased abundance of proteins related to translation, protease inhibition, and photosynthesis. On the other hand, infestation caused increased abundance of proteins involved in protein modification and degradation. Our results also suggest that S. oryzae infestation interferes with intracellular transport, DNA structure maintenance, and amino acid and lipid metabolism in rice leaves. Proteomic data were positively correlated with enzymatic assays and RT-qPCR analysis. Our findings describe the protein expression patterns of late-infested rice leaves and suggest several targets which could be tested in future biotechnological approaches aiming to avoid the population increase of phytophagous mite in rice plants.

Oryza brachyantha A. Chev. et Roehr

The growing interest in the Oryza genus comes from the feasibility of studying genome evolution of these closely related species, as well as the direct impact of identifying desirable phenotypes that could be transferred to Oryza sativa, one of the world’s most important cereals. Among the Oryza species, Oryza brachyantha is unique: it is highly divergent, has the smallest genome in the genus and is the only FF species, and has several traits that could be useful to improve Oryza sativa. However, our understanding of the basic biology of O. brachyantha and conservation of its diversity in germplasm are still preliminary. In this chapter, we summarize the current knowledge on O. brachyantha, especially on its recently published genomes (nuclear and chloroplastidic), basic genetics, and sequence comparisons with other Oryza species. The information gathered here should be useful to guide efforts to conserve and explore O. brachyantha diversity, a necessary step in order to achieve both basic and applied science goals in the future.

Crops responses to mite infestation: it’s time to look at plant tolerance to meet the farmers’ needs

Graduate Program in Biotechnology, University of Taquari Valley, Lajeado, Brazil, Biological Sciences and Health Center, University of Taquari Valley, Lajeado, Brazil, Graduate Program in Biotechnology, University of Caxias do Sul, Caxias do Sul, Brazil, Graduate Program in Agrobiology, Federal University of Santa Maria, Santa Maria, Brazil, Graduate Program in Cell and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil

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.