Auxin Response Factor Genes Repertoire in Mulberry: Identification, and Structural, Functional and Evolutionary Analyses

Vinay Baranwal,Nisha Negi,Paramjit Khurana

doi:10.3390/genes8090202

Abstract

Auxin Response Factors (ARFs) are at the core of the regulation mechanism for auxin-mediated responses, along with AUX/IAA proteins.They are critical in the auxin-mediated control of various biological responses including development and stress. A wild mulberry species genome has been sequenced and offers an opportunity to investigate this important gene family. A total of 17 ARFs have been identified from mulberry (Morus notabilis) which show a wide range of expression patterns. Of these 17 ARFs, 15 have strong acidic isoelectric point (pI) values and a molecular mass ranging from 52 kDa to 101 kDa. The putative promoters of these ARFs harbour cis motifs related to light-dependent responses, various stress responses and hormone regulations suggestive of their multifactorial regulation. The gene ontology terms for ARFs indicate their role in flower development, stress, root morphology and other such development and stress mitigation related activities. Conserved motif analysis showed the presence of all typical domains in all but four members that lack the PB1 domain and thus represent truncated ARFs. Expression analysis of these ARFs suggests their preferential expression in tissues ranging from leaf, root, winter bud, bark and male flowers. These ARFs showed differential expression in the leaf tissue of M. notabilis, Morus laevigata and Morus serrata. Insights gained from this analysis have implications in mulberry improvement programs.

Highlights

Auxin—a phytohormone—has been shown to regulate many aspects of plant development, especially in apical dominance, root initiation, shoot elongation and shaping the pattern of embryos, etc
A total of 17 Auxin Response Factors (ARFs) encoding genes have been identified in the M. notabilis genome
ARFs were identified in mulberry and they have made clades with truncated ARFs of Arabidopsis

Summary

Introduction

Auxin—a phytohormone—has been shown to regulate many aspects of plant development, especially in apical dominance, root initiation, shoot elongation and shaping the pattern of embryos, etc. Several downstream genes have been identified including SMALL AUXIN UP RNA (SAUR), Gretchen Hagen 3 (GH3) and the indole-3-acetic acid-inducible gene (Aux/IAA) [2]. Structural analysis of these ARFs has revealed three conserved features including an N-terminal DNA-binding domain, a less conserved transcriptional regulation domain and the C-terminal protein interaction domain are involved in hetero or oligomerization. The DNA binding domain binds to ARE elements directly by virtue of its structural topology, while the protein interaction domain at the C-terminal leads either to homodimerization or binding to other AUX/IAA, facilitating the transcriptional block of these ARFs [3,4]. Several truncated ARFs that lack C-terminal motifs have been reported [5]

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Conclusion