Análise comparativa do transcriptoma e de metabólitos em resposta ao déficit hídrico em Eucalyptus spp.

Abstract

Over the decades, several molecular and physiological studies have shown that responses to water deficit depend on an integrated regulatory network, which involves all aspects of plants. These plant responses vary according to the severity of the plant's stress, genotype and developmental phase and help to reduce the deleterious effects of lack of water and confer tolerance to this condition. As these differences can be detected in nearby species, this work aimed to obtain a multidisciplinary view of the responses generated by two eucalyptus clones under conditions of low water availability, focusing on the transcriptional, biochemical and physiological mechanisms activated in this situation. The clones analyzed were VM01 (Eucalyptus urophylla x E. camaldulensis) and VM05 (E. urophylla), selected by presenting

contrasting responses under water deficit. Comparisons at the transcriptional level with RNA- seq data revealed differentially expressed genes and transcriptional factors responsive to water

deficit in the two genetic materials analyzed. The relative expression of genes involved in biosynthesis, transport and degradation of abscisic acid (ABA) was modulated in response to the treatments imposed, mainly in vascular roots and tissues. Similar pattern was detected in routes of carbon metabolism, where the activity of specific enzymes was altered in situations of severe stress, with difference between clones VM01 and VM05. More specific studies of genes from the NCED, DREB and MET families, associated with regulation of water deficit in several species, revealed that there are several genes in eucalyptus with potential use in future studies on water scarcity. Gene expression analysis by RT-qPCR of genes from these families revealed that clones adopt different strategies to survive under limiting conditions, and VM05 appears to be under control of epigenetic modifications. To help elucidate this idea, water deficit signaling metabolites were quantified in leaf tissues of the two clones. Differences were detected in the metabolism of carbohydrates (starch, reducing sugars and sucrose) and ABA content, suggesting that clone VM01 presents faster defense responses to water reduction, a fact that reflects in a higher tolerance of these plants to the water deficit. In general, the integrated and comparative analyzes of these clones allowed for a better understanding of the regulatory mechanism of water deficit in eucalyptus, with the generation of data that guarantee future studies and help the breeding programs in the selection of genotypes tolerant to stress.