Identification and Characterization of Cotton Genes Involved in Fuzz‐Fiber Development

Abstract

Cotton fuzz fibers, like Arabidopsis trichomes, are elongated unicells. It is postulated that a transcriptional complex of GLABRA1 (GL1), GLABRA3 (GL3), and TRANSPARENT TESTAGLABRA1 (TTG1) might be in existence in Arabidopsis as evidenced by their physical interaction in yeast, and the complex regulates expression of GLABRA2 (GL2) controlling trichome cell differentiation; it is also assumed that TRIPTYCHON (TRY) and CAPRICE (CPC) counteract the complex formation in neighboring cells. Here, the homologs GaMYB23 (a homolog of GL1), GaDEL65 (a homolog of GL3), GaTTG1, GaCPC and GaTRY were identified in Gossypium arboreum. We show that GaMYB23 can bind to and activate the promoters of GaCPC, GaGL2 and GaTRY, and that GaMYB23, GaTRY and GaTTG1 could interact with GaDEL65 in yeast and in planta. In situ analysis showed that GaMYB23, GaGL2, GaDEL65, and GaTRY were predominantly expressed in fuzz fiber, but GaTRY proteins were primarily found in undeveloped epidermal cells. A G. arboreum fuzzless mutant with consistently high level GaMYB23 transcript has lost the detectable GaMYB23‐promoter of GaGL2 complex, corresponding to sharply reduced transcription of GaGL2. Our results support that cotton homologs to the genetic molecules regulating Arabidopsis trichome differentiation interacted in the epidermis of ovules and the redundant GaMYB23 serves as a negative regulator in fuzz‐fiber patterning.

GhJAZ2 negatively regulates cotton fiber initiation by interacting with the R2R3‐MYB transcription factor GhMYB25‐like

“…The TRY protein interacts with GL1 and GL3 or EGL3 to inhibit R2R3‐MYB/bHLH/WD40 transcription complex formation, thereby suppressing trichome initiation. When the cotton genes GaDEL65 , GaDEL61 and GaMYB23 (which are homologous to GL3/EGL3 or GL1 ) are transferred into Arabidopsis gl3 or gl1 mutants, trichome production is rescued (Wang et al ., ). The class IV HD‐ZIP family transcription factor GaHOX1 (a homolog of GL2) can rescue the glabrous phenotype of the Arabidopsis mutant gl2‐2 .…”

Genome-wide identification and characterization of JAZ gene family in upland cotton (Gossypium hirsutum)

“…Additionally, JAZ interacts with GL3 and GL1 to regulate JA-mediated trichome initiation in Arabidopsis 39 . Similarly, GhMYB2 and GaMYB23 (GL1 homolog), GhTTG1/GhTTG3 and GaDEL65 (GL3 homolog) are preferentially expressed in initiated fiber cells of cotton and may regulate cotton fiber initiation and differentiation 31–37, 40, 41 . Several R2R3-type MYB TFs also were reported to be involved in cotton fiber initiation.…”

Silencing the vacuolar invertase gene GhVIN1 blocks cotton fiber initiation from the ovule epidermis, probably by suppressing a cohort of regulatory genes via sugar signaling

“…However, understanding of the control of fiber initiation is still in its infancy. Nevertheless, a cohort of MYB transcription factors (Pu et al ., ; Machado et al ., ; Walford et al ., ; Wang et al ., ) and an auxin biosynthesis gene, iaaM (Zhang et al ., ), have been identified as required for cotton fiber initiation. However, the regulatory pathways controlling expression of these fiber initiation genes remain unknown, and the many other components that have been predicted to be required for de novo patterning of the cotton ovule epidermis are yet to be identified (Wilkins and Arpat, ; Ruan, ).…”