Biology subjects

Ricachenevsky, F. K.

Publications and source records attributed to Ricachenevsky, F. K..

3 recordsLinked to original sources

bioRxiv2020

Cold tolerance in rice plants is partially controlled by root responses

Rice (Oryza sativa L.) ssp. indica is the most cultivated species in the South of Brazil. However, these plants face low temperature stress from September to November, which is the period of early sowing, affecting plant development during the initial stages of growth, and reducing rice productivity. This study aimed to characterize the root response to low temperature stress during the early vegetative stage of two rice genotypes contrasting in their cold tolerance (CT, cold-tolerant; and CS, cold-sensitive). Root dry weight and length, as well as number of root hairs, were higher in CT than CS when exposed to cold treatment. Histochemical analyses indicated that roots of CS genotype present higher levels of lipid peroxidation and H2O2 accumulation, along with lower levels of plasma membrane integrity than CT under low temperature stress. RNAseq analyses revealed that the contrasting genotypes present completely different molecular responses to cold stress. The number of over-represented functional categories was lower in CT than CS under cold condition, suggesting that CS genotype is more impacted by low temperature stress than CT. Several genes might contribute to rice cold tolerance, including the ones related with cell wall remodeling, cytoskeleton and growth, signaling, antioxidant system, lipid metabolism, and stress response. On the other hand, high expression of the genes SRC2 (defense), root architecture associated 1 (growth), ACC oxidase, ethylene-responsive transcription factor, and cytokinin-O-glucosyltransferase 2 (hormone-related) seems to be related with cold sensibility. Since these two genotypes have a similar genetic background (sister lines), the differentially expressed genes found here can be considered candidate genes for cold tolerance and could be used in future biotechnological approaches aiming to increase rice tolerance to low temperature.

plant biology↗

bioRxiv2020

Nipponbare and wild rice species as unexpected tolerance and susceptibility sources against Schizotetranychus oryzae (Acari: Tetranychidae) mite infestation

Cultivated rice (Oryza sativa L.) is frequently exposed to multiple stresses, including Schizotetranychus oryzae mite infestation. Rice domestication has narrowed the genetic diversity of the species, reducing the stress resistance and leading to a wide susceptibility. Therefore, wild rice species present an alternative to search for this lost variability. Aiming to observe the response of two wild rice species (Oryza barthii and Oryza glaberrima) and two Oryza sativa genotypes (cv. Nipponbare and O. sativa f. spontanea) to S. oryzae infestation, we used agronomic, physiological and molecular analyses. Surprisingly, analyses of leaf damage, histochemistry, chlorophyll concentration and chlorophyll fluorescence showed that the wild species present higher level of leaf damage, increased accumulation of H2O2 and lower photosynthetic capacity when compared to O. sativa genotypes under infested conditions. Infestation did not affect plant height, but decreased tiller number, except in cv. Nipponbare, whose development was not affected. Infestation also caused the death of wild plants during the reproductive stage, unlike O. sativa genotypes, which were able to tolerate stress and produce seeds. While infestation did not affect the weight of 1,000 grains in both O. sativa genotypes, the number of panicles per plant was affected only in O. sativa f. spontanea, and the percentage of full seeds per panicle and seed length were increased only in cv. Nipponbare. Proteomic analysis allowed us to identify 195 differentially abundant proteins when comparing susceptible (O. barthii) and tolerant (O. sativa cv. Nipponbare) genotypes under control and infested conditions. We found that O. barthii has a less abundant antioxidant arsenal. In addition, it is unable to modulate proteins involved with general metabolism and energy production under infested condition. In Nipponbare we found high abundance of detoxification-related proteins, general metabolic processes and energy production, which allows us to suggest that, under infested condition, the primary metabolism is maintained more active compared to O. barthii. Also, Nipponbare presents a greater abundance of defense-related proteins, such as osmotin, ricin B-like lectin, and protease inhibitors of the Bowman Birk trypsin inhibitor family, as well as higher levels of the compatible osmolyte Proline under infested condition. Identification of these differentially abundant proteins can be used as an important biotechnological tool in breeding programs that aim increased tolerance to phytophagous mite infestation.

plant biology↗

bioRxiv2019

The Mitochondrial Iron Regulated (MIR) gene is Oryza genus-specific and evolved before the speciation of major AA-genome lineages

Rice (Oryza sativa L.) is both a model species and an economically relevant crop. The Oryza genus comprises 25 species, which constitute a genetic reservoir for cultivated rice breeding. Genomic data is available for several Oryza species, making it a good model for genetics and evolution within closely related species. The Mitochondrial Iron Regulated (MIR) gene was previously implicated in O. sativa Fe deficiency response, and was considered an orphan gene present only in rice. Here we show that MIR is also found in other Oryza species that belong to the AA genome group. We characterized the evolutionary pattern of MIR genes within the Oryza genus. Our data suggest that MIR originated de novo from non-coding sequences present only in AA genome species, but these sequences in turn are derived from an exon fragment of Raffinose Synthase genes, present in several groups of monocots. We also show that all species that have a putative functional MIR conserve their regulation by Fe deficiency, with the exception of Oryza barthii. In O. barthii, the MIR coding sequence was translocated to a different chromosomal position and separated from its regulatory region, which led to a lack of Fe deficiency responsiveness. Moreover, we show that MIR co-expression subnetwork cluster in O. sativa is responsive to Fe deficiency, evidencing the importance of the newly originated gene in Fe uptake. This work establishes that MIR is not an orphan gene as previously proposed, but a de novo originated gene within the Oryza genus. We also showed that MIR is undergoing genomic changes in at least one species (O. barthii), which can impact its role in Fe deficiency.

plant biology↗