Gh JAZ 2 negatively regulates cotton fiber initiation by interacting with the R2R3‐ MYB transcription factor Gh MYB 25‐like

Jasmonic acid ( JA ) signaling has been well studied in Arabidopsis. Most reports focus on the role of JA in biological pathways, such as stress resistance, trichome initiation and anthocyanin accumulation. The JASMONATE ZIM ‐ DOMAIN ( JAZ ) protein is one of the important repressors in the JA signaling pathway. Previous studies showed that JA functions in fiber initiation and elongation, but little is known about how JAZ genes function in fiber development. In this study, a cotton JAZ protein (Gh JAZ 2) containing a highly conserved TIFY motif and a C‐terminal Jas domain was identified, and its function during cotton fiber development was analysed. Gene expression analysis showed that Gh JAZ 2 was preferentially expressed in the root, hypocotyl, flower and ovule 1 day before anthesis. Overexpression of Gh JAZ 2 inhibited both lint and fuzz fiber initiation, and reduced the fiber length. Yeast two‐hybrid assays showed that Gh JAZ 2 interacted with the R2R3‐ MYB transcription factors Gh MYB 25‐like and Gh GL 1, the bHLH transcription factor Gh MYC 2, the WD repeat protein Gh WD 40 and the unknown protein Gh JI 1. Among these transcription factors, previous studies showed that downregulation of Gh MYB 25‐like leads to a fiberless phenotype in cotton seeds. Molecular and genetic evidence showed that the Gh JAZ 2 protein suppresses fiber initiation in the overexpressing lines by interacting with Gh MYB 25‐like and suppressing Gh MYB 25‐like activity. Our results suggested that Gh JAZ 2 functions as a primary transcription repressor during lint and fuzz fiber initiation by interacting with Gh MYB 25‐like, Gh GL 1, Gh MYC 2, Gh WD 40 and Gh JI 1 to regulate the JA signaling pathway. The plant hormone Jasmonic Acid was known to be involved in fiber initiation and elongation, but the molecular details were not fully elucidated. Here we show that a jasmonate ZIM‐domain (JAZ) protein inhibits lint and fuzz fiber initiation by repressing the transcriptional activation of MYB‐like and bHLH transcription factors and other genes in the JA signaling pathway.