Analysis of the Genes from Gibberellin, Jasmonate, and Auxin Signaling Under Drought Stress: A Genome-Wide Approach in Castor Bean (Ricinus communis L.)

Castor bean (Ricinus communis L.) can tolerate long periods of dehydration, allowing the investigation of gene circuits involved in drought tolerance. Genes from gibberellins, jasmonates, and auxin signaling are important for crosstalk in the developmental and environmental adaptation process to drought conditions. However, the genes related to these signals, as well as their transcription profiles under drought, remain poorly characterized in the castor bean. In the present work, genes from gibberellins, jasmonates, and auxin signaling were identified and molecularly characterized. These analyses allowed us to identify genes encoding receptors, inhibitory proteins, and transcription factors from each signaling pathway in the castor bean genome. Chromosomal distribution, gene structure, evolutionary relationships, and conserved motif analyses were performed. Expression analysis through RNA-seq and RT-qPCR revealed that gibberellins, jasmonates, and auxin signaling were modulated at multiple levels under drought, with notable changes in specific genes. The gibberellin receptor RcGID1c was downregulated in response to drought, and RcDELLA3 was strongly repressed, whereas its homologues were not, reinforcing the suggestion of a nuanced regulation of gibberellin signaling during drought. Considering jasmonate signaling, the downregulation of the transcription factor RcMYC2 aligned with the drought tolerance observed in mutants lacking this gene. Altogether, these analyses have provided insights into hormone signaling in the castor bean, unveiling transcriptional responses that enhance our understanding of high drought tolerance in this plant. This knowledge opens avenues for identifying potential candidate genes suitable for genetic manipulation in biotechnological approaches.