Comparative Dynamic Transcriptome Reveals the Delayed Secondary-Cell-Wall Thickening Results in Altered Lint Percentage and Fiber Elongation in a Chromosomal Segment Substitution Line of Cotton (Gossypium hirsutum L.).

Yang Gao,Yu Chen,Han Zhao,Tianzhen Zhang,Wanyu Lv,Zhangqiang Song,Ling Zheng,Jingxia Zhang,Jun Zhang,Furong Wang,Xuehan Huo

doi:10.3389/fpls.2021.756434

Abstract

Lint percentage (LP) is an important yield component in cotton that is usually affected by initial fiber number and cell wall thickness. To explore how fiber cell wall development affects LP, phenotypic identification and dynamic transcriptome analysis were conducted using a single segment substitution line of chromosome 15 (SL15) that harbors a major quantitative trait locus (QTL) for LP. Compared to its recurrent parent LMY22, SL15 did not differ in initial fiber number, but the fiber cell wall thickness and single-fiber weight decreased significantly, altering LP. The comparative transcriptome profiles revealed that the secondary cell wall (SCW) development phase of SL15 was relatively delayed. Meanwhile, the expression of genes related to cell expansion decreased more slightly in SL15 with fiber development, resulting in relatively higher expression at SL15_25D than at LMY22_25D. SCW development-related genes, such as GhNACs and GhMYBs, in the putative NAC-MYB-CESA network differentially expressed at SL15_25D, along with the lower expression of CESA6, CSLC12, and CSLA2. The substituted chromosomal interval was further investigated, and found 6 of 146 candidate genes were differentially expressed in all four cell development periods including 10, 15, 20 and 25 DPA. Genetic variation and co-expression analysis showed that GH_D01G0052, GH_D01G0099, GH_D01G0100, and GH_D01G0140 may be important candidate genes associated with qLP-C15-1. Our results provide novel insights into cell wall development and its relationship with LP, which is beneficial for lint yield and fiber quality improvement.

Highlights

Cotton (Gossypium spp.) is a principal source of natural fiber
The results showed that 98.97% of the genetic composition of substitution line of chromosome 15 (SL15) originated from LMY22, while the remaining 1.03% was from Chr. 15 of LY343, suggesting that the genetic background of SL15 was almost the same as LMY22 except for the segment of Chr. 15 (Supplementary Figure 1)
A 4-year field trial showed that the Lint percentage (LP) of SL15 was significantly reduced, and fiber length (FL) was remarkably increased (1.1–1.4 mm) (Figures 1A–C), the other fiber-related traits, namely fiber strength, micronaire and fuzz content not different (Supplementary Figures 2, 3)

Summary

Introduction

Cotton (Gossypium spp.) is a principal source of natural fiber. To fulfill the fiber needs of the ever-increasing global population, it is essential to improve cotton yield (Tilman et al, 2011). Cotton lint yield is constituted of three important components: boll number, seed cotton weight per boll, and lint percentage (LP, determined as lint weight [LW, g]/seed cotton weight [g] × 100). Of these components, LP is notable for being more stable across different environments (Muhammad et al, 2006; Su et al, 2016), and is an important component for cotton yield (Wang et al, 2014). Several studies on improving LP have taken a quantitative genetics approach, identifying associated quantitative trait locus (QTLs) in different populations (Yu et al, 2013; Wang et al, 2014, 2016). Additional genome-wide association studies (GWASs) have been carried out to identify stable QTLs or critical genes associated with agronomic traits of interest (Fang et al, 2017b; Sun et al, 2018; Song et al, 2019; Su et al, 2019), identifying several candidate genes having functional roles closely related to LP (Su et al, 2016, 2019; Sun et al, 2018)

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Results

Conclusion