Cotton KNL1, encoding a class II KNOX transcription factor, is involved in regulation of fibre development.

Si-Ying Gong,Yang Li,Xue-Bao Li,Li Zhou,Xiang Sun,Li-Xia Qin,Geng-Qing Huang

doi:10.1093/jxb/eru182

Si-Ying Gong, Yang Li + Show 5 more

Open Access

https://doi.org/10.1093/jxb/eru182

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Abstract

In this study, the GhKNL1 (KNOTTED1-LIKE) gene, encoding a classical class II KNOX protein was identified in cotton (Gossypium hirsutum). GhKNL1 was preferentially expressed in developing fibres at the stage of secondary cell wall (SCW) biosynthesis. GhKNL1 was localized in the cell nucleus, and could interact with GhOFP4, as well as AtOFP1, AtOFP4, and AtMYB75. However, GhKNL1 lacked transcriptional activation activity. Dominant repression of GhKNL1 affected fibre development of cotton. The expression levels of genes related to fibre elongation and SCW biosynthesis were altered in transgenic fibres of cotton. As a result, transgenic cotton plants produced aberrant, shrunken, and collapsed fibre cells. Length and cell-wall thickness of fibres of transgenic cotton plants were significantly reduced compared with the wild type. Furthermore, overexpression and dominant repression of GhKNL1 in Arabidopsis resulted in a reduction in interfascicular fibre cell-wall thickening of basal stems of transgenic plants. Complementation revealed that GhKNL1 rescued the defective phenotype of Arabidopsis knat7 mutant in some extent. These data suggest that GhKNL1, as a transcription factor, participates in regulating fibre development of cotton.

Highlights

The plant cell wall is a complex and dynamic structure that regulates cell growth and provides structural and mechanical support to the plant, and acts as a barrier against the environment and potentially organisms (Somerville et al, 2004)
Motif scan analysis identified that GhKNL1 consisted of four conserved domains: MEINOX domain, which could be divided into two subdomains (KNOX1 and KNOX2), a GSE domain, a ELK domain, and a homeodomain (Supplementary Fig. S1A available at JXB online)
Plant knotted-like homeobox protein (KNOX) proteins belong to a large conserved family which can be divided into three groups based on phylogenetic clustering (Hake et al, 2004; Magnani and Hake, 2008)

Summary

Introduction

The plant cell wall is a complex and dynamic structure that regulates cell growth and provides structural and mechanical support to the plant, and acts as a barrier against the environment and potentially organisms (Somerville et al, 2004). After cessation of cell growth, SCW is deposited inside the PCW in certain cell types, such as fibres and tracheary elements. A highly elongated and thickened single cell derived from the ovule epidermis, provides an excellent system for study on cell elongation and SCW biosynthesis (Kim and Triplett, 2001; Haigler et al, 2012). Fibre development includes four distinct and overlapping stages: initiation, elongation (PCW biosynthesis), SCW biosynthesis/thickening, and maturation. Cellulose is abundantly synthesized and deposited on cell walls in an orderly manner at the SCW stage (Wilkins and Arpat, 2005). Final dry weight can be attributed to 95% cellulose (Timpa and Triplett, 1993)

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