Control of cotton fibre elongation by a homeodomain transcription factor GhHOX3

Abstract

Cotton fibres are unusually long, single-celled epidermal seed trichomes and a model for plant cell growth, but little is known about the regulation of fibre cell elongation. Here we report that a homeodomain-leucine zipper (HD-ZIP) transcription factor, GhHOX3, controls cotton fibre elongation. GhHOX3 genes are localized to the 12th homoeologous chromosome set of allotetraploid cotton cultivars, associated with quantitative trait loci (QTLs) for fibre length. Silencing of GhHOX3 greatly reduces (>80%) fibre length, whereas its overexpression leads to longer fibre. Combined transcriptomic and biochemical analyses identify target genes of GhHOX3 that also contain the L1-box cis-element, including two cell wall loosening protein genes GhRDL1 and GhEXPA1. GhHOX3 interacts with GhHD1, another homeodomain protein, resulting in enhanced transcriptional activity, and with cotton DELLA, GhSLR1, repressor of the growth hormone gibberellin (GA). GhSLR1 interferes with the GhHOX3–GhHD1 interaction and represses target gene transcription. Our results uncover a novel mechanism whereby a homeodomain protein transduces GA signal to promote fibre cell elongation.

The two domains of cotton WLIM1a protein are functionally divergent

“…Recently, significant progress has been made in large-scale identification of genes and proteins involved in fiber development, particularly of those related to fiber elongation and secondary wall deposition (Arpat et al, 2004;Cao, 2015;Gou et al, 2007;Jin et al, 2013;Shi et al, 2006;Zhao et al, 2010). Moreover, a number of fiber development-related genes have been structurally or functionally characterized (Han et al, 2013;Li et al, 2005;Pei, 2015;Ruan et al, 2003;Shan et al, 2014;Xu et al, 2013;Zhang et al, 2011). These studies have made important progress towards understanding the molecular mechanisms governing cotton fiber development.…”

Whole genome sequencing of cotton—a new chapter in cotton genomics

“…Fiber length is a key factor determining cotton quality with the yield of cotton fiber depends mainly on the number of fiber cells of each ovule. Phytohormones, including ethylene and gibberellins (GA), are proposed to regulate cotton fiber initiation and elongation [4,5]. Comparative genomics analysis revealed that neither extremely high level of ethylene in D genome nor low level in A genome is beneficial to cotton fiber development, which suggest that fine-tuning of ethylene biosynthesis is necessary for normal cotton fiber cell elongation and maturation.…”

The homeodomain-containing transcription factor, GhHOX3, is a key regulator of cotton fiber elongation

“…This research uncovers the molecular mechanism of GA Figure 1 (color online) A model for regulation of cotton fiber elongation by GhHOX3 and the phytohormone GA [1]. A, In cotton fibers, DELLA proteins bind to HOX3 to prevent its binding to other HD-ZIP transcription factors, repressing their transcriptional activation to target genes.…”

“…Recently, Chen and colleagues from Shanghai Institute of Plant Physiology and Ecology of Chinese Academy of Sciences, in collaboration with scientists from Nanjing Agricultural University and from the US, have identified a homeodomain (HOX)-containing transcription factor that plays a central role in controlling cotton fiber elongation [1].…”

“…Based on genetic analysis, Shan et al [1] discovered that GhHOX3 gene, which encoded an HD-ZIP IV transcription factor, associated with fiber quality traits, particularly the fiber length. Silencing of GhHOX3 gene resulted in a dramatic decrease of fiber length (>80% decrease, lint completely disappeared), while fiber initiation was largely unaffected.…”