Fig. 9

A model of MC-regulated lateral root formation in cotton. MC inhibits GA biosynthesis by down-regulating CPS, GA20oxs, and GA3ox and up-regulating GA2ox. MC down-regulates GID1 to activate DELLA and XERICO, the inducer in ABA biosynthesis; furthermore, down-regulated ABAH decreases the oxidative degradation of ABA, promoting ABA accumulation. Meanwhile, MC activates ABA signaling by up-regulating its receptor PYL8, which induces the expression of MYB44 and ARF7, likely promoting the expression of WRKY23 to activate auxin signaling. Auxin transport genes LAX and PIN are up-regulated to regulate auxin maxima in the lateral root initiation zone. Up-regulated YUC and AAO increase auxin biosynthesis. Auxin-induced degradation of IAA14 de-represses ARF7/19 to induce LBD16/18, which is responsible for the activation of E2Fa/b to promote the first asymmetric cell divisions. Moreover, auxin increases the expression of CYCD and CDKA to regulate the G1-to-S transition, CDKA/B and CYCA/B to regulate the G2-to-M transition, and CDCs, FKBP, and CYP to regulate mitosis. In conclusion, our data suggest that MC orchestrates GA and ABA metabolism, which further regulates auxin signaling, transport, and biosynthesis to control the cell division responsible for lateral root formation