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The RAF‐like mitogen‐activated protein kinase kinase kinases RAF22 and RAF28 are required for the regulation of embryogenesis in Arabidopsis
Author(s) -
Wang Bo,
Liu Guting,
Zhang Jing,
Li Yuan,
Yang Hailian,
Ren Dongtao
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14063
Subject(s) - suspensor , biology , microbiology and biotechnology , arabidopsis , kinase , protein kinase a , cell fate determination , embryonic stem cell , polar auxin transport , embryo , auxin , embryogenesis , mutant , genetics , somatic embryogenesis , gene , transcription factor
Summary 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 RAF 22 and RAF 28, two RAF ‐like mitogen‐activated protein kinase kinase kinases ( MAPKKK s) in Arabidopsis, are involved in the regulation of embryogenesis. The double knockout mutant of RAF 22 and RAF 28 was embryo lethal. A large proportion of the raf22 −/− raf28 +/− mutant embryos exhibited various defects, including disordered proembryo cell divisions, disruption of the bilaterally symmetrical structure, abnormally formative divisions of hypophysis and exaggerated suspensor growth. Whereas the kinase active form of RAF 22 could complement these embryonic aberrant phenotypes, the kinase inactive form could not. The restrictive expression of the basal cell fate marker WOX 8 in the abnormally dividing suspensor cells and the apical cell linage marker WOX 2 in the abnormal proembryos indicated that apical and basal cell fates were unchanged in the abnormal embryos. The polar distribution of the auxin maxima and the PIN 1 and PIN 7 auxin transporters was markedly altered in the abnormal embryos. Our results suggest that RAF 22 and RAF 28 are important components of embryogenesis and that auxin polar transport may be involved in this regulation.