LEAFY COTYLEDON1-CASEIN KINASE I-TCP15-PHYTOCHROME INTERACTING FACTOR4 Network Regulates Somatic Embryogenesis by Regulating Auxin Homeostasis  

Abstract

Somatic embryogenesis (SE) is an efficient tool for the propagation of plant species and also, a useful model for studying the regulatory networks in embryo development. However, the regulatory networks underlying the transition from nonembryogenic callus to somatic embryos during SE remain poorly understood. Here, we describe an upland cotton (Gossypium hirsutum) CASEIN KINASE I gene, GhCKI, which is a unique key regulatory factor that strongly affects SE. Overexpressing GhCKI halted the formation of embryoids and plant regeneration because of a block in the transition from nonembryogenic callus to somatic embryos. In contrast, defective GhCKI in plants facilitated SE. To better understand the mechanism by which GhCKI regulates SE, the regulatory network was analyzed. A direct upstream negative regulator protein, cotton LEAFY COTYLEDON1, was identified to be targeted to a cis-element, CTTTTC, in the promoter of GhCKI. Moreover, GhCKI interacted with and phosphorylated cotton CINCINNATAlike TEOSINTE BRANCHED1-CYCLOIDEA-PCF transcription factor15 by coordinately regulating the expression of cotton PHYTOCHROME INTERACTING FACTOR4, finally disrupting auxin homeostasis, which led to increased cell proliferation and aborted somatic embryo formation in GhCKI-overexpressing somatic cells. Our results show a complex process of SE that is negatively regulated by GhCKI through a complex regulatory network.

Laccase GhLac1 Modulates Broad-Spectrum Biotic Stress Tolerance via Manipulating Phenylpropanoid Pathway and Jasmonic Acid Synthesis

“…To determine the role of GhLac1 in plant cell wall regeneration, protoplasts were isolated from YZ1 or the GhLac1 overexpression lines embryogenic calli according to previous methods (Min et al, 2015) and transferred to a cell wall regeneration medium described by Yang et al (2007). The visualization of cell wall regeneration was performed as described by Yang et al (2008).…”

GbSOBIR1 confers Verticillium wilt resistance by phosphorylating the transcriptional factor GbbHLH171 in Gossypium barbadense

“…Cell-free protein expression and in vitro kinase assays were performed as previously reported (Min et al, 2015). The cell-freeexpressed kinase GbSOBIR1 and the E. coli-induced andexpressed substrate GbbHLH171-GST were mixed with kinase assay buffer (40 mM HEPES, pH 7.5, 130 mM KCl, 10 mM MgCl 2 , 0.1 mM ATP, 5 mM dithiothreitol, 5 mM b-glycerophosphate and 0.2 mM sodium orthovanadate).…”

GhL1L1 affects cell fate specification by regulating GhPIN1‐mediated auxin distribution

“…It was then divided to three regions: À1174 to À1953-bp region containing two CCAAT boxes (at approximately À1838, À1500 bp) named A, À800 to À1173-bp region containing a G-box motif (at approximately À977 bp) named B and À1 to À799-bp region containing basic promoter elements without the CCAAT-box motif and G-box named C. Three vectors of the promoters were constructed in the pHis-1 bait vector, with proGhPP2AA2-DC representing deletion of the A region, proGhPP2AA2-DG representing deletion of the B region and ProGhPP2AA2-mG representing mutation of the B region (Gbox, CACGTT mutated to CAAGGT). The Y1H assay was performed as previously described (Min et al, 2015). The primers used in the Y1H assay are listed in Table S1.…”

“…GhHmgB3-deficient hypocotyls dedifferentiate more rapidly but fail to differentiate into ECs (Hu et al, 2011). By contrast, overexpression of GhCKI prevents EC and plant regeneration by blocking the transition from NECs to ECs (Min et al, 2015). However, the precise mechanisms of gene regulation during cotton SE have not been elucidated.…”

“…FUS3 interacts with LEC2 to promote auxin biosynthesis (Tang et al, 2017). Disruption of auxin homeostasis by GhCKI overexpression, which might act downstream of GhLEC1, leads to defective embryogenesis (Min et al, 2015).…”