Predição e anotação de miRNAs e o papel dos fatores de transcrição na resposta de Elaeis guineensis Jacq. aos estresses abióticos de seca e salinidade

Abstract

The oil palm (Elaeis guineensis Jacq.) is an oilseed crop of great economic importance and can yield up to 10 times more oil than other oilseed crops, such as soybean and canola. In 2021/2022, the world consumed approximately 82 million tons of palm oil and palm kernel oil, and as demand increases, expanding the yield is necessary. In Brazil, there is an extensive area suitable for planting oil palm; however, these areas go through long periods of drought, requiring artificial irrigation to be sustainable. Around 30% of the world's irrigated farmland is damaged by salinity, negatively affecting crop productivity. So, to expand oil palm cultivation to such areas in Brazil, one must better understand the response of this oilseed crop to drought and salinity stresses. MicroRNAs (miRNAs) are directly related to the post-transcriptional regulation of gene expression and are essential molecules in the plant response to abiotic stress. Our group performed a study to understand how this oilseed crop responds to two abiotic stresses by predicting and characterizing miRNAs in young oil palms exposed to drought and salinity and then performing the characterization of a select group of transcription factors responsive to both stresses. We collected leaf samples from young oil palm trees - subjected or not to salt stress (12 days) and water deprivation (14 days) - and performed RNA-seq and smallRNA-seq. The smallRNA-seq data underwent rigorous curation using mireap version 0.2, Shortstack version 3.4 and psRNA-Target and subsequent analysis of differential expression and functional annotation using appropriate software, while RNA-seq data underwent extensive analysis of structural and functional annotation and differential expression analysis using qPCR. The sequencing data generated allowed the identification of putative miRNA target genes in the oil palm's genome and to further understand the roles of these regulatory genes in response to stress. Seventy-nine and 81 miRNAs appeared under salinity and drought stress, respectively, with 52 known and 29 new miRNAs. Functional annotation of the putative target genes of differentially expressed miRNAs under salt and water stress revealed several transcription factors. A group of 20 transcription factors - differentially expressed in the leaves of young oil palm plants under both stresses - were selected and further characterized, showing 23 distinct domains and seven conserved motifs in the coding regions, in addition to seven cis-acting elements related to the stress response in the promoter region. Overexpression or knockout of such genes resulted in tolerance to these abiotic stresses in other plant species. The results presented here show a similar expression pattern to both abiotic stresses indicating that these genes may play essential roles in plant adaptation to stress. Our research suggests that these genes should be validated in planta as candidate genes in a genetic improvement program focused on crop resistance to drought and salinity stress.