A comprehensive characterization and expression profiling of defensin family peptides in Arabidopsis thaliana with a focus on their abiotic stress-specific transcriptional modulation

In addition to defensins, plants possess an array of defensin-like peptides that share many of their characteristics, as well as a role in plant's innate immunity. Their involvement in the response to pathogens is well-known but the contribution in the plant response to abiotic stimuli is not fully understood. We have undertaken an in silico analysis to characterize all defensin family genes hitherto found in Arabidopsis, including genes encoding for defensin-like peptides, by detecting several peptides as candidates for further studies aiming to decipher specific responses to biotic and abiotic stresses, as well as to their crosstalk. We performed several analyses, including co- expression and cis-regulatory elements analyses, using transcriptomic data obtained from the ARS database, which integrates more than 20,000 Arabidopsis RNA-seq libraries. In silico analysis showed that jasmonates and ABA, together with transcription factors belonging to WRKY and AP2/EREBP families, modulate defensin and defensin-like gene expression. Indeed, the analysis performed in this study allowed to extract and organize omics data, which finally supported the inducible nature of defensins under both abiotic and biotic stresses. Moreover, in vivo expression analyses confirmed the heat and drought responsiveness of PDF1.4, , ATTI1, , PDF1.1, , DEFL 206, , defensin family genes selected for being upregulated by several abiotic conditions, at transcriptional level. Finally, the co-expression analysis provided information on other biological processes that may be correlated to the defensin induction, such as maintaining ROS homeostasis. Combining the comprehensive analysis of different transcriptional datasets with the integration of in vivo analyses emerged as a robust methodological approach to assess the proposed multi-stress responsive nature of defensin family genes.