Berberine enhances defects in the establishment of leaf polarity in asymmetric leaves1 and asymmetric leaves2 of Arabidopsis thaliana

Ayami Nakagawa,Nobuo Sato,Chiyoko Machida,Shoko Kojima,Byung Yoon Cha,Yasunori Machida,Gorou Horiguchi,Je-Tae Woo,Kazuomi Ohga,Hirokazu Tsukaya,Kazuo Nagai,Hiro Takahashi

doi:10.1007/s11103-012-9929-7

Ayami Nakagawa, Nobuo Sato + Show 10 more

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https://doi.org/10.1007/s11103-012-9929-7

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Abstract

Leaves develop as flat lateral organs from the indeterminate shoot apical meristem. The establishment of polarity along three-dimensional axes, proximal–distal, medial–lateral, and adaxial–abaxial axes, is crucial for the growth of normal leaves. The mutations of ASYMMETRIC LEAVES1 (AS1) and AS2 of Arabidopsis thaliana cause defects in repression of the indeterminate state and the establishment of axis formation in leaves. Although many mutations have been identified that enhance the adaxial–abaxial polarity defects of as1 and as2 mutants, the roles of the causative genes in leaf development are still unknown. In this study, we found that wild-type plants treated with berberine produced pointed leaves, which are often observed in the single mutants that enhance phenotypes of as1 and as2 mutants. The berberine-treated as1 and as2 mutants formed abaxialized filamentous leaves. Berberine, an isoquinoline alkaloid compound naturally produced in various plant sources, has a growth inhibitory effect on plants that do not produce berberine. We further showed that transcript levels of meristem-specific class 1 KNOX homeobox genes and abaxial determinant genes were increased in berberine-treated as1 and as2. Berberine treated plants carrying double mutations of AS2 and the large subunit ribosomal protein gene RPL5B showed more severe defects in polarity than did the as2 single mutant plants. We suggest that berberine inhibits (a) factor(s) that might be required for leaf adaxial cell differentiation through a pathway independent of AS1 and AS2. Multiple pathways might play important roles in the formation of flat symmetric leaves.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-012-9929-7) contains supplementary material, which is available to authorized users.

Highlights

Leaves develop as flat lateral organs from the shoot apical meristem, and the establishment of polarity along threedimensional axes, proximal–distal, medial–lateral and adaxial–abaxial, is crucial for the growth of normal leaves (Steeves and Sussex 1989; Hudson 2000; Tsukaya 2006; Bowman and Floyd 2008; Szakonyi et al 2010)
We found that berberine affected the establishment of leaf polarity in the as1 or as2 mutant plants of A. thaliana
Berberine might inhibit a function(s) of a novel factor(s) that is involved in adaxialization independently from ASYMMETRIC LEAVES1 (AS1)–AS2 during leaf development

Summary

Introduction

Leaves develop as flat lateral organs from the shoot apical meristem, and the establishment of polarity along threedimensional axes, proximal–distal, medial–lateral and adaxial–abaxial, is crucial for the growth of normal leaves (Steeves and Sussex 1989; Hudson 2000; Tsukaya 2006; Bowman and Floyd 2008; Szakonyi et al 2010). AS1 encodes a myb domain protein and AS2 encodes a plant-specific protein with an AS2/LOB domain, both of which are nuclear proteins (Byrne et al 2000; Iwakawa et al 2002). These proteins form a complex structure (Yang et al 2008) (hereinafter referred to as AS1–AS2) that is involved in the establishment of proper axis formation. Some mutations of genes alter leaf patterning and axis formation in the absence of either AS1 or AS2: namely, ribosomal protein genes, genes involved in chromatin remodeling, histone modification, and small RNA biogenesis, and others

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