|Bo Wang, Guting Liu, Jing Zhang, Yuan Li, Hailian Yang, and Dongtao Ren. The RAF-like mitogen-activated protein kinase kinase kinasesRAF22 and RAF28 are required for the regulation ofembryogenesis in Arabidopsis. The plant journal. DOI: 10.1111/tpj.14063|
The RAF-like mitogen-activated protein kinase kinase kinasesRAF22 and RAF28 are required for the regulation ofembryogenesis in Arabidopsis
Bo Wang, Guting Liu, Jing Zhang, Yuan Li, Hailian Yang, and Dongtao Ren
The plant journal
In Arabidopsis, embryonic development follows a stereotypical pattern of cell division. Although many factors have been reported to participate in establishment of the proper embryonic pattern, the molecular mechanisms underlying pattern formation are unclear. In this study we showed that RAF22 and RAF28, two RAF-like mitogen-activated protein kinase kinase kinases (MAPKKKs) in Arabidopsis, are involved in the regulation of embryogenesis. The double knockout mutant of RAF22and RAF28was embryo lethal. A large proportion of the raf22_/_raf28+/_mutant embryos exhibited various defects, including disordered proembryocell divisions, disruption of the bilaterally symmetrical structure, abnormally formative divisions ofhypophysis and exaggerated suspensor growth. Whereas the kinase active form of RAF22 could complementthese embryonic aberrant phenotypes, the kinase inactive form could not. The restrictive expressionof the basal cell fate marker WOX8 in the abnormally dividing suspensor cells and the apical cell linage markerWOX2 in the abnormal proembryos indicated that apical and basal cell fates were unchanged in theabnormal embryos. The polar distribution of the auxin maxima and the PIN1 and PIN7 auxin transporterswas markedly altered in the abnormal embryos. Our results suggest that RAF22 and RAF28 are importantcomponents of embryogenesis and that auxin polar transport may be involved in this regulation.