Comprehensive Analysis and Functional Studies of WRKY Transcription Factors in Nelumbo nucifera.

Jing Li,Siqi Gao,Yi Li,Mei Yang,E Tapio Palva,Xianbao Deng,Dong Yang,Qi Yin,Yacen Xiong,Shiqi Ye

doi:10.3390/ijms20205006

Abstract

The WRKY family is one of the largest transcription factor (TF) families in plants and plays central roles in modulating plant stress responses and developmental processes, as well as secondary metabolic regulations. Lotus (Nelumbo nucifera) is an aquatic crop that has significant food, ornamental and pharmacological values. Here, we performed an overview analysis of WRKY TF family members in lotus, and studied their functions in environmental adaptation and regulation of lotus benzylisoquinoline alkaloid (BIA) biosynthesis. A total of 65 WRKY genes were identified in the lotus genome and they were well clustered in a similar pattern with their Arabidopsis homologs in seven groups (designated I, IIa-IIe, and III), although no lotus WRKY was clustered in the group IIIa. Most lotus WRKYs were functionally paired, which was attributed to the recently occurred whole genome duplication in lotus. In addition, lotus WRKYs were regulated dramatically by salicilic acid (SA), jasmonic acid (JA), and submergence treatments, and two lotus WRKYs, NnWRKY40a and NnWRKY40b, were significantly induced by JA and promoted lotus BIA biosynthesis through activating BIA biosynthetic genes. The investigation of WRKY TFs for this basal eudicot reveals new insights into the evolution of the WRKY family, and provides fundamental information for their functional studies and lotus breeding.

Highlights

The WRKY family is among the 10 largest transcription factor (TF) families in higher plants and is found throughout the green lineage [1]
After removing overlaps and those without WRKY domains, a total of 65 NnWRKY genes were identified from the lotus genome of ‘China Antique’ (ASM303368v1) [37]
These NnWRKY genes are unevenly distributed in the eight lotus chromosomes, with 16 genes on chromosome 1 (Chr 1), and 11, 11, 8, 8, 5, 5 genes on chromosomes 2, 3, 4, 5, 6, 8, respectively, while only a single gene was identified on Chr 7 (Table S1)

Summary

Introduction

The WRKY family is among the 10 largest transcription factor (TF) families in higher plants and is found throughout the green lineage [1]. The WRKY TFs derive their name from their characteristic WRKY DBD, which comprises approximately 60 amino acids and a highly conserved sequence of WRKYGQK in the N-terminal together with a novel C2H2 or C2HC zinc finger motif in the C-terminal. Besides the core sequence of WRKYGQK, there are several other heptapeptide variants, such as WRKYGKK, WKKYGQK, WRKYGRK, WRKYGEK and WSKYEQK [2,3]. Both the WRKY and the Zinc finger motif are believed to be crucial for proper DNA binding [4]. Based on the number of WRKY domains and the features of the zinc finger motifs, WRKY TFs are classified into three distinct groups. The conservation of the WRKY gene family was shown by its high binding affinity to W box (C/TTGACT/C) [5,9], altered binding preference to WK box (TTTTCCAC) and WT box (GGACTTTC) have been reported [10,11,12]

Methods

Results

Conclusion