Characterization of cotton ARF factors and the role of GhARF2b in fiber development

Abstract

Background Cotton fiber is a model system for studying plant cell development. At present, the functions of many transcription factors in cotton fiber development have been elucidated, however, the roles of auxin response factor (ARF) genes in cotton fiber development need be further explored. Results Here, we identify auxin response factor (ARF) genes in three cotton species: the tetraploid upland cotton G. hirsutum, which has 73 ARF genes, and its putative extent parental diploids G. arboreum and G. raimondii, which have 36 and 35 ARFs, respectively. Ka and Ks analyses revealed that in G. hirsutum ARF genes have undergone asymmetric evolution in the two subgenomes. The cotton ARFs can be classified into four phylogenetic clades and are actively expressed in young tissues. We demonstrate that GhARF2b, a homolog of the Arabidopsis AtARF2, was preferentially expressed in developing ovules and fibers. Overexpression of GhARF2b by a fiber specific promoter inhibited fiber cell elongation but promoted initiation and, conversely, its downregulation by RNAi resulted in fewer but longer fiber. We show that GhARF2b directly interacts with GhHOX3 and represses the transcriptional activity of GhHOX3 on target genes. Conclusion Our results uncover an important role of the ARF factor in modulating cotton fiber development at the early stage.

Transcriptome Time-Course Analysis in the Whole Period of Cotton Fiber Development

“…Biosynthesis and signal transduction pathways that mediate the effects of phytohormones are quite essential for fiber development in cotton ( Kim and Triplett, 2001 ; Ahmed et al, 2018 ). In the previous studies, auxin could promote fiber initiation and fiber units when applied to the ovules exogenously ( Gialvalis and Seagull, 2001 ), and GhARF2b , a homolog of the AtARF2 , shows a predominant expression in the cotton fiber tissue, and it negatively influences cotton fiber elongation but promotes fiber initiation ( Zhang et al, 2021a ). In the Gh-Cluster2-Blue module, which is associated with –3 DPA, the ARF gene GH_A06G0864 probably had an impact on the number of epidermal cell protrusions in the initial stage of cotton fiber development.…”

Comprehensive identification and expression analysis of CRY gene family in Gossypium

“…Analyses were performed with SYBR-Green PCR Mastermix (TaKaRa) on a cycler (Mastercycler RealPlex; Eppendorf Ltd, Shanghai, China). The G. hirsutum histone-3 ( GhHIS3 ) genes were used as internal references [ 81 , 86 ], and the relative amount of amplified product was calculated following the 2 −∆∆Ct method [ 87 ]. For the G. hirsutum samples, relative expression levels among different stresses were normalized by calibrating with the leaves sample from the wild plants.…”

Molecular Mechanisms of Plant Trichome Development

“…A yeast two-hybrid analysis showed that GhCPC can interact with the bHLH-type protein GhMYC1, and GhMYC1 can also interact with GhTTG1 and GhTTG4 . GhCPC negatively regulates early fiber initiation and elongation through the CPC-MYC1-TTG1/4 complex ( Liu et al, 2015 ; Zhang et al, 2021d ). In the 35S :GhCPC transgenic line, the transcription levels of downstream genes GhHOX3 and GhRDL1 decreased significantly compared to in the wild type ( Deng et al, 2012a ).…”

“…However, RNAi lines of GhARF2b resulted in fiber reduction but lengthening compared with that in the wild type. GhARF2b directly interacts with GhHOX3 and inhibits the transcriptional activity of GhHOX3 on target genes ( Zhang et al, 2021d ). GhARF2-1 and GhARF18-1 are only expressed in trichomes, and overexpression of these two genes in Arabidopsis enhances trichome initiation ( Xiao et al, 2018 ).…”