Genome-Scale Analysis of the WRI-Like Family in Gossypium and Functional Characterization of GhWRI1a Controlling Triacylglycerol Content.

Xinshan Zang,Xingli Li,Jianjiang Ma,Jiwen Yu,Nuohan Wang,Yanhui Geng,Wenfeng Pei,Dan Li,Jinfa Zhang,Man Wu,Yupeng Cui,Guoyuan Liu

doi:10.3389/fpls.2018.01516

Abstract

Cotton (Gossypium spp.) is the most important natural fiber crop and the source of cottonseed oil, a basic by-product after ginning. AtWRI1 and its orthologs in several other crop species have been previously used to increase triacylglycerols in seeds and vegetative tissues. In the present study, we identified 22, 17, 9, and 11 WRI-like genes in G. hirsutum, G. barbadense, G. arboreum, and G. raimondii, respectively. This gene family was divided into four subgroups, and a more WRI2-like subfamily was identified compared with dicotyledonous Arabidopsis. An analysis of chromosomal distributions revealed that the 22 GhWRI genes were distributed on eight At and eight Dt subgenome chromosomes. Moreover, GhWRI1a was highly expressed in ovules 20–35 days after anthesis and was selected for further functional analysis. Ectopic expression of GhWRI1a rescued the seed phenotype of a wri1-7 mutant and increased the oil content of Arabidopsis seeds. Our comprehensive genome-wide analysis of the cotton WRI-like gene family lays a solid foundation for further studies.

Highlights

Cotton, especially upland cotton (Gossypium hirsutum L.), is the main source of renewable textile fibers and is well known for its oil-rich seeds
Numerous studies have revealed a crucial role for WRI-like genes in TAG biosynthesis, including GhWRI1 corresponding to GhWRI1b (Liu et al, 2018)
We have accomplished the first-ever identification of WRI-like genes in four representative types of cotton, i.e., allotetraploid cotton species G. hirsutum and G. barbadense and their diploid ancestors G. arboreum, and G. raimondii

Summary

Introduction

Especially upland cotton (Gossypium hirsutum L.), is the main source of renewable textile fibers and is well known for its oil-rich seeds. The homozygous atwri mutant has a wrinkled seed phenotype and exhibits an 80% reduction in seed oil content compared with wild type (WT) Arabidopsis (Focks and Benning, 1998; Cernac and Benning, 2004). Expression of AtWRI1 cDNA under the control of the cauliflower mosaic virus 35S-promoter has been found to lead to increased seed oil content and the accumulation of TAGs in developing seedlings (Cernac and Benning, 2004). In rapeseed, overexpression of WRI1-like (BnWRI1) cDNAs driven by cauliflower mosaic virus 35S-promoter results in 10–40% increased seed oil content and enlarged seed size and mass in 51 transgenic Arabidopsis lines (Liu et al, 2010). Expression of CsWRI1A, B, or C has rescued the seed phenotype of the Arabidopsis wri loss-of-function mutant (An et al, 2017)

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Conclusion