Key points are not available for this paper at this time.
Precise regulation of cell division is essential for proper tissue patterning in multicellular organisms. In Arabidopsis , the ground tissue (GT) comprises cortex and endodermis in the early stages of root development. During GT maturation, additional periclinal cell divisions (PCDs) occasionally occur of the endodermis, generating a middle cortex (MC) layer between the cortex and endodermis. Although several regulatory proteins and phytohormones were identified to mediate GT patterning, such as SHORT-ROOT (SHR), SCARECROW (SCR), CYCLIND6;1 (CYCD6;1), and gibberellins (GAs), the interrelationship among these factors is not elucidated. Here, we report that three closely related receptor-like kinases (RLKs), ARH1, FEI1, and FEI2, play crucial roles in mediating a signal transduction pathway from the SHR-SCR module to GA to regulate GT patterning. Two independent triple mutants of these RLKs ( tri-1 and tri-2 ) exhibit increased MC formation compared with wild type. Genetic analysis indicated that all three RLKs regulate MC formation mainly in a cell-autonomous manner. The transcription levels of these RLKs are negatively controlled by SHR and SCR. The altered GT patterns in shr and scr can be partially complemented by tri-1 . GA biosynthesis is significantly reduced in the roots of tri-1 . The excessive MC formation in tri-1 can be greatly suppressed by the exogenous application of GA 3 or by the mutation of CYCD6;1 . Our results demonstrate a signaling pathway involving SHR/SCR-ARH1/FEI1/FEI2-GA-CYCD6;1 to govern GT patterning in Arabidopsis thaliana .
Chang et al. (Tue,) studied this question.