Abstract
The ERECTA family genes, ERECTA (ER), ERECTA-LIKE1 (ERL1), and ERECTA-LIKE2 (ERL2), encode leucine-rich repeat receptor-like kinases in Arabidopsis thaliana. Knocking out these three genes can cause severe phenotypes, which indicates that they play significant roles in plant growth and development. However, the molecular mechanism within remains unclear. Here we show that the short hypocotyl phenotypes of er erl1 erl2 mutants are mainly due to the defects of cell elongation rather than the cell division. In contrast, in the ERECTA overexpression transgenic plants, the hypocotyl length is increased with elongated cells. Moreover, we show that the er erl1 erl2 triple mutant contains a low level of auxin, and the expression levels of the key auxin biosynthesis genes are significantly reduced. Consistent with this observation, increasing exogenous or endogenous auxin levels could partially rescue the cell elongation defects of the er erl1 erl2 triple mutant. Therefore, our results provide a molecular basis for auxin mediated ERECTA control of the hypocotyl length in Arabidopsis thaliana.
Highlights
Plant cell size is one of the most important features in plant morphology, which is controlled strictly by the inheritance and influenced by the external environment
Little is known about the genetic interaction between the ERECTA and auxin signaling in control of the hypocotyl development
Our results show that the endogenous auxin levels were dramatically reduced in the hypocotyl of the er erl1 erl2 triple mutant (Figures 2A–D)
Summary
Plant cell size is one of the most important features in plant morphology, which is controlled strictly by the inheritance and influenced by the external environment. The growth of hypocotyls in Arabidopsis is the elongation and division of hypocotyl cells in essence. The morphological structure of Arabidopsis thaliana hypocotyl is simple, consisting of more than 20 cells in longitudinal direction, which is below cotyledons to the above of radicle. Because most of these cells are formed in the embryonic stage, only a few are produced by cell division after germination, suggests that the hypocotyl growth is mainly caused by the cell elongation (Gendreau et al, 1997). The hypocotyl of Arabidopsis has become an important model system for studying plant cell elongation due to its simple structure and important physiological functions
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