Genome-wide exploration of auxin response factors (ARFs) and their expression dynamics in response to abiotic stresses and growth regulators in coconut (Cocos nucifera L.)

Abstract

Auxin response factors (ARFs) are a class of transcription factors with the ability to bind specifically to the promoter region of auxin-responsive genes in plants and thereby modulate various aspects of biological processes and responses to diverse environmental conditions. Identification and characterization of ARF gene families have been undertaken in various plant species; however, no such data, delineating ARFs in coconut, is available. Through genome-wide analysis, we have identified 20 CnARF (Cocos nucifera ARF) genes in the genome of a dwarf cultivar, Chowghat Green Dwarf. Evolutionary analysis of CnARFs, along with ARFs from oil palm and date palm, showed that palm ARFs could be classified into three major clades. Multiple sequence alignment and analysis of conserved motifs revealed that majority of the CnARFs harbored all the three principal domains (i.e. N-terminus DNA binding domain, an ARF sub-domain and an AUX/IAA sub-domain), which are characteristic of all plant ARFs. Quantitative real-time PCR-based expression analysis of ARFs of mature zygotic embryos, exposed to osmotic and temperature stresses and growth regulators, suggest a complex and stress-specific transcriptional response of coconut embryo-derived ARFs. Collectively, these findings offer valuable information and the first molecular insights into the CnARFs, laying the foundation for further functional characterization in developmental and reproductive pathways and their inclusion in breeding for stress tolerance in coconut.