The MYB transcription factor GhMYB25 regulates early fibre and trichome development

Abstract

SUMMARYLittle is still known about the developmental control of the long seed coat trichomes of cotton (Gossypium hirsutum L.). In Arabidopsis, leaf trichome initiation is regulated by a group of well-defined transcription factors that includes MYB and homeodomain types. Many MYBs are expressed in fibres, but their roles in fibre development remain unclear. We analysed the function of one MYB transcription factor, GhMYB25, identified from transcriptome comparisons between wild-type and fibreless cotton mutants. A GhMYB25 promoter-GUS construct in transgenic cotton was expressed in the epidermis of ovules, developing fibre initials and fibres, in the trichomes of a number of tissues including leaves, stems and petals, as well as in the anthers, pollen and the epidermal layers of roots and root initials, but not in root hairs. Cotton is an allotetraploid with two very similar GhMYB25 genes that were silenced by a single RNAi construct. GhMYB25-silenced cotton showed alterations in the timing of rapid fibre elongation, resulting in short fibres, dramatic reductions in trichomes on other parts of the plant, and reductions in seed production. Reciprocal crosses between transgenic and nontransgenic plants indicated that pollen and ovule viability per se were not disrupted. Ectopic over-expression of GhMYB25 had more subtle impacts, with increases in cotton fibre initiation and leaf trichome number. High expression appeared to adversely affect fertility. Our results provide convincing evidence for a role of GhMYB25, like other MIXTA-like MYBS, in regulating specialized outgrowths of epidermal cells, including, in this case, cotton fibres.

Genetic Mapping in Cotton

“…Cotton seed hair development has a strong resemblance with Arabidopsis leaf trichome development [109]. The data generated from different studies using cotton fiberrelated genes supported this study, thus confirmed the close relationship between cotton seed fibers and Arabidopsis trichomes [110][111][112].…”

The Cotton Transcription Factor TCP14 Functions in Auxin-Mediated Epidermal Cell Differentiation and Elongation

“…Likewise, transcription factors participating in cotton fiber development have been reported by several studies. For example, a few MYB transcription factors were found to play important roles in cotton fiber initiation (Cedroni et al, 2003;Suo et al, 2003;Wang et al, 2004;Pu et al, 2008;Machado et al, 2009;Guan et al, 2011;Walford et al, 2011). In addition, it was recently reported that GbTCP (from sea-island cotton), which shares 47% protein sequence identity with GhTCP14, is involved in cotton fiber development, possibly through JA signaling (Hao et al, 2012).…”

The Hairless Stem Phenotype of Cotton (Gossypium barbadense) Is Linked to aCopia-Like Retrotransposon Insertion in aHomeodomain-Leucine ZipperGene (HD1)

“…GhMYB25 belongs to a MIXTA type MYB transcription factor family and controls cotton fiber initiation. GhHOX3, a homologous gene of Arabidopsis HDG11/12, regulates plant epidermal cell differentiation (Nakamura et al 2006;Machado et al 2009). Significantly reduced gene expression of GbMYB25 and GbHOX3 in the TE-inserted cottons provided further evidence that GhHD1 is a critical upstream gene of GhMYB25 (Bedon et al 2014) and GbHOX3.…”