Long-term transcriptional memory in rice plants submitted to salt shock.

MAIN CONCLUSION: A first salt shock event alters transcriptional and physiological responses to a second event, being possible to identify 26 genes associated with long-term memory. Soil salinity significantly affects rice cultivation, resulting in large losses in growth and productivity. Studies report that a disturbing event can prepare the plant for a subsequent event through memory acquisition, involving physiological and molecular processes. Therefore, genes that provide altered responses in subsequent events define a category known as "memory genes". In this work, the RNA-sequencing (RNA-Seq) technique was used to analyse the transcriptional profile of rice plants subjected to different salt shock events and to characterise genes associated with long-term memory. Plants subjected to recurrent salt shock showed differences in stomatal conductance, chlorophyll index, electrolyte leakage, and the number of differentially expressed genes (DEGs), and they had lower Na+/K+ ratios than plants that experienced only one stress event. Additionally, the mammalian target of rapamycin (mTOR) pathways, and carbohydrate and amino acid-associated pathways were altered under all conditions. Memory genes can be classified according to their responses during the first event (+ or -) and the second shock event (+ or -), being possible to observe a larger number of transcripts for groups [+ /-] and [-/ +], genes characterised as "revised response." This is the first long-term transcriptional memory study in rice plants under salt shock, providing new insights into the process of plant memory acquisition.

Indução de resistência em arroz contra Bipolaris oryzae Breda de Hann, através da expressão constitutiva de um gene de quitinase / Induction of resistance in rice against Bipolaris oryzae Breda de Hann by constitutive expression of achitinase gene

Este trabalho objetivou a transformação genética da cultivar de arroz BRS Taim, para obtenção de resistência ao fungo Bipolaris oryzae, agente da mancha parda. Para a transformação das plantas foi utilizada a cepa LBA 4404 de Agrobacterium tumefaciens transformada com o plasmídeo pMOG 22 que codifica o gene da quitinase do fungo entomopatogênico Metarhizium anisopliae. Mesocótilos de arroz foram imersos por 30 min. em solução bacteriana (OD600 = 0,7), contendo acetoceringona (100 Mm). Após os explantes foram co-cultivados por 72 horas em meio MS sem hormônio. Para seleção dos transformantes foi utilizado meio MS com 5 mg L-1 de BAP e 15 mg L-1 de higromicina, incubados a 25±1°C, fotoperíodo de 16 horas e densidade de fluxo de fótons de 42 µmol m-2 s-1. Foram obtidas 5 plantas transformadas, perfazendo uma média de eficiência de transformação de 1,53 %. A resistência das plantas foi observada somente por um dos isolados. Os resultados permitem concluir que as plantas de arroz transformadas com o gene da quitinase(Chit 1)podem reduzir o desenvolvimento do fungo B. oryzae, porém existe uma diferença na reação entre isolados.

This study aimed at a rice transformation for resistance to Bipolaris oryzae causal organism of Brown Spot, the cultivar BRS Taim and the line LBA 4404 of Agrobacterium tumefaciens transformed with plasmid pMOG 22 that codifies the chitinasegene Metarhizium anisopliae was used. Rice mesocotils immersed for 30 min in bacterial solution of OD600 = 0,7 with acetoceringone (100Mm), were co-cultivated for 72 hours in MS medium free of hormones and with 100Mm of acetoceringone. Mesocotils were then transferred to MS with 5mg L-1 de BAP and15 mg L-1 of higromicin for 45 days at 25°C and 16 ligth hours. The five transformed plants obtained (1,53 transformation rate) were inoculated with two B. oryzae isolates.Resistance was observed only with one of the isolates. The results indicate that rice plants transformed with chitinase gene (Chit 1)can reduce the colonization by some isolates of B. oryzae.