Characterization of temperature-sensitive mutants reveals a role for receptor-like kinase SCRAMBLED/STRUBBELIG in coordinating cell proliferation and differentiation during Arabidopsis leaf development

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Abstract

The balance between cell proliferation and cell differentiation is essential for leaf patterning. However, identification of the factors coordinating leaf patterning and cell growth behavior is challenging. Here, we characterized a temperature-sensitive Arabidopsis mutant with leaf blade and venation defects. We mapped the mutation to thesub-2allele of theSCRAMBLED/STRUBBELIG (SCM/SUB) receptor-like kinase gene whose functions in leaf development have not been demonstrated. Thesub-2mutant displayed impaired blade development, asymmetric leaf shape and altered venation patterning under high ambient temperature (30°C), but these defects were less pronounced at normal growth temperature (22°C). Loss ofSCM/SUBfunction results in reduced cell proliferation and abnormal cell expansion, as well as altered auxin patterning.SCM/SUBis initially expressed throughout leaf primordia and becomes restricted to the vascular cells, coinciding with its roles in early leaf patterning and venation formation. Furthermore, constitutive expression of theSCM/SUBgene also restricts organ growth by inhibiting the transition from cell proliferation to expansion. We propose the existence of a SCM/SUB-mediated developmental stage-specific signal for leaf patterning, and highlight the importance of the balance between cell proliferation and differentiation for leaf morphogenesis.

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