The miR319-Targeted GhTCP4 Promotes the Transition from Cell Elongation to Wall Thickening in Cotton Fiber

Abstract

Plant cell growth involves a complex interplay among cell-wall expansion, biosynthesis, and, in specific tissues, secondary cell wall (SCW) deposition, yet the coordination of these processes remains elusive. Cotton fiber cells are developmentally synchronous, highly elongated, and contain nearly pure cellulose when mature. Here, we report that the transcription factor GhTCP4 plays an important role in balancing cotton fiber cell elongation and wall synthesis. During fiber development the expression of miR319 declines while GhTCP4 transcript levels increase, with high levels of the latter promoting SCW deposition. GhTCP4 interacts with a homeobox-containing factor, GhHOX3, and repressing its transcriptional activity. GhTCP4 and GhHOX3 function antagonistically to regulate cell elongation, thereby establishing temporal control of fiber cell transition to the SCW stage. We found that overexpression of GhTCP4A upregulated and accelerated activation of the SCW biosynthetic pathway in fiber cells, as revealed by transcriptome and promoter activity analyses, resulting in shorter fibers with varied lengths and thicker walls. In contrast, GhTCP4 downregulation led to slightly longer fibers and thinner cell walls. The GhHOX3-GhTCP4 complex may represent a general mechanism of cellular development in plants since both are conserved factors in many species, thus providing us a potential molecular tool for the design of fiber traits.

The Regulation of CIN-like TCP Transcription Factors

“…Cotton fibers are specific trichome types on the seed epidermis. The constitutive overexpression of GhTCP4 homologous to Arabidopsis TCP4 in upland cotton ( Gossypium hirsutum ) repressed the elongation of cotton fiber [ 78 ]. However, CIN-like TCPs positively regulate hypocotyl cell elongation in Arabidopsis .…”

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

“…The study of cotton fiber development regulation provides not only valuable knowledge to understanding plant cell growth and cell wall biosynthesis, but also candidate genes for cotton molecular breeding [4]. To date a number of genes that function in cotton fiber cells have been identified, including homeodomain transcription factor GaHOX1, GhHOX3 and GhHD1 [5][6][7], bHLH transcription factor GhPRE1 [8], KNOX transcription factor knl1 [9], the sterol carrier gene [10], MYB transcription factors GhMYB25, GhMYB25-like, GhMML3 and GhMML4 [11][12][13][14], NAC transcription factor fsn1 [15], transcription factor WLIM1a gene [16], sucrose synthase gene [17], cotton actin1 gene [18], cotton BURP domain protein GhRDL1 [19], ethylene pathway related genes [20], fasciclin-like arabinogalactan protein, Ghfla1 [21], and TCP transcription factor GhTCP4 [22] etc. Among recent progresses are the characterizations of transcription factors which regulate the major events of cotton fiber development, such as MYBs and HD-ZIP IVs involved in cotton fiber initiation and elongation, as well as a number of other types of factors.…”

“…The MIXTA type MYB transcription factors (GhMYB25, GhMYB25-like and GhMML4_D12) are master regulators of cotton fiber initiation [11,13,14] and lint fiber development [12], whereas the HD-ZIP IV transcription factor GhHOX3 plays a pivotal role in controlling fiber elongation [5], whose activity is regulated by the phytohormone gibberellin. In addition, NAC (GhFSN1) and TCP4 transcription factors positively regulates secondary cell wall biosynthesis [15,22]. However, cotton fiber growth and development are complex processes involving cell differentiation, cell skeleton orientation growth, cell wall synthesis, and so on [23].…”

Characterization of Cotton ARF Factors and the Role of GhARF2b in Fiber Development

“…The study of cotton ber development regulation provides not only valuable knowledge to understanding plant cell growth and cell wall biosynthesis, but also candidate genes for cotton molecular breeding. To date a number of genes that function in cotton ber cells have been identi ed, including homeodomain transcription factor GaHOX1, GhHOX3 and GhHD1 [4][5][6], bHLH transcription factor GhPRE1 [7], KNOX transcription factor knl1 [8], the sterol carrier gene [9], MYB transcription factors GhMYB25, GhMYB25-like, GhMML3 and GhMML4 [10][11][12][13], NAC transcription factor fsn1 [14], transcription factor WLIM1a gene [15], sucrose synthase gene [16], cotton actin1 gene [17], cotton BURP domain protein GhRDL1 [18], ethylene pathway related genes [19], fasciclin-like arabinogalactan protein, Gh a1 [20], and TCP transcription factor GhTCP4 [21] etc. Among recent progresses are the characterizations of transcription factors which regulate the major events of cotton ber development, such as MYBs and HD-ZIP IVs involved in cotton ber initiation and elongation, as well as a number of other types of factors.…”

“…The MIXTA type MYB transcription factors (GhMYB25, GhMYB25-like and GhMML4_D12) are master regulators of cotton ber initiation [10,12,13] and lint ber development [11], whereas the HD-ZIP IV transcription factor GhHOX3 plays a pivotal role in controlling ber elongation [4], whose activity is regulated by the phytohormone gibberellin. In addition, NAC (GhFSN1) and TCP4 transcription factors positively regulates secondary cell wall biosynthesis [14,21]. However, cotton ber growth and development are complex processes involving cell differentiation, cell skeleton orientation growth, cell wall synthesis, and so on [22].…”