AKR2A participates in the regulation of cotton fibre development by modulating biosynthesis of very-long-chain fatty acids.

Wenjun Hu,Chunyan Sun,Hong Zhang,Guoxin Shen,Hongling Lu,Yuqi Hou,Rongbin Hu,Jia Wei,Xiao Han,Chunquan Zhu,Lin Chen,Yifan Cai,Guochang Sun,Fuguang Li,Xiongfeng Ma,Zuoren Yang,Xiaoyun Qiu

doi:10.1111/pbi.13221

Abstract

SummaryThe biosynthesis of very‐long‐chain fatty acids (VLCFAs) and their transport are required for fibre development. However, whether other regulatory factors are involved in this process is unknown. We report here that overexpression of an Arabidopsis gene ankyrin repeat‐containing protein 2A (AKR2A) in cotton promotes fibre elongation. RNA‐Seq analysis was employed to elucidate the mechanisms of AKR2A in regulating cotton fibre development. The VLCFA content and the ratio of VLCFAs to short‐chain fatty acids increased in AKR2A transgenic lines. In addition, AKR2A promotes fibre elongation by regulating ethylene and synergizing with the accumulation of auxin and hydrogen peroxide. Analysis of RNA‐Seq data indicates that AKR2A up‐regulates transcript levels of genes involved in VLCFAs’ biosynthesis, ethylene biosynthesis, auxin and hydrogen peroxide signalling, cell wall and cytoskeletal organization. Furthermore, AKR2A interacted with KCS1 in Arabidopsis both in vitro and in vivo. Moreover, the VLCFA content and the ratio of VLCFAs to short‐chain fatty acids increased significantly in seeds of AKR2A‐overexpressing lines and AKR2A/KCS1 co‐overexpressing lines, while AKR2A mutants are the opposite trend. Our results uncover a novel cotton fibre growth mechanism by which the critical regulator AKR2A promotes fibre development via activating hormone signalling cascade by mediating VLCFA biosynthesis. This study provides a potential candidate gene for improving fibre yield and quality through genetic engineering.

Highlights

The Arabidopsis ankyrin repeat-containing protein 2A (AKR2A) was initially isolated as a GF14k-interacting protein involved in directing proteins to the correct cellular membranes after translation (Shen et al, 2010)
We used the cauliflower mosaic virus (CaMV) 35S promoter to drive the expression of a full-length AKR2A cDNA and introduced the DNA construct into
AKR2A-2 and AKR2A-57, were found to have increased levels of AKR2A based on Western blot analysis (Figure S1b), and DNA blot analysis confirmed that these two lines did contain the transgene AKR2A (Figure S1c)

Summary

Introduction

The Arabidopsis ankyrin repeat-containing protein 2A (AKR2A) was initially isolated as a GF14k-interacting protein involved in directing proteins to the correct cellular membranes after translation (Shen et al, 2010). Bae et al (2008) reported that AKR2A functions as an essential molecular chaperone in the biogenesis of chloroplast outer envelope membrane (OEM) proteins. Knockout mutants of AKR2A, akr2a-1 to akr2a-3, in Arabidopsis contain greatly reduced levels of OEM proteins and have defects in chloroplast biogenesis, suggesting that AKR2A functions as a cytosolic facilitator for sorting and targeting nascent chloroplast OEM proteins to chloroplast and serves as a chaperone for OEM proteins (Bae et al, 2008). The binding of AKR2A to the AKR2A-binding sequence of new membrane proteins keeps these proteins in insertion-competent state before they are sent to their specific destinations (Shen et al, 2010; Zhang et al, 2010)

Results

Discussion

Conclusion