Atkinesin-13A modulates cell-wall synthesis and cell expansion in Arabidopsis thaliana via the THESEUS1 pathway.

Ushio Fujikura,Thomas Laux,Kim Findlay,Staffan Persson,Alexander Ivakov,Lore Elsaesser,Michael Lenhard,Clara Sánchez-Rodríguez,Holger Breuninger,Alice Cheung

doi:10.1371/journal.pgen.1004627

Abstract

Growth of plant organs relies on cell proliferation and expansion. While an increasingly detailed picture about the control of cell proliferation is emerging, our knowledge about the control of cell expansion remains more limited. We demonstrate here that the internal-motor kinesin AtKINESIN-13A (AtKIN13A) limits cell expansion and cell size in Arabidopsis thaliana, with loss-of-function atkin13a mutants forming larger petals with larger cells. The homolog, AtKINESIN-13B, also affects cell expansion and double mutants display growth, gametophytic and early embryonic defects, indicating a redundant role of the two genes. AtKIN13A is known to depolymerize microtubules and influence Golgi motility and distribution. Consistent with this function, AtKIN13A interacts genetically with ANGUSTIFOLIA, encoding a regulator of Golgi dynamics. Reduced AtKIN13A activity alters cell wall structure as assessed by Fourier-transformed infrared-spectroscopy and triggers signalling via the THESEUS1-dependent cell-wall integrity pathway, which in turn promotes the excess cell expansion in the atkin13a mutant. Thus, our results indicate that the intracellular activity of AtKIN13A regulates cell expansion and wall architecture via THESEUS1, providing a compelling case of interplay between cell wall integrity sensing and expansion.

Highlights

Growth of plant lateral organs to their characteristic sizes is based on cell proliferation and on cell expansion [1]
Mutations in AtKINESIN-13A change petal size In an EMS-mutagenesis screen in the Landsberg erecta (Ler) background for mutations with altered petal size, we identified a line with larger petals (Fig. 1A)
RT-PCR analysis indicated that atkin13a-3 plants express full-length AtKIN13A mRNA, whereas no full-length transcript can be detected in mutants for the T-DNA insertion allele atkin13a-4 (Fig. S2A)

Summary

Introduction

Growth of plant lateral organs to their characteristic sizes is based on cell proliferation and on cell expansion [1]. In a first phase of organ growth cells throughout the primordium increase in size and divide mitotically. Our knowledge about the factors regulating cell expansion in growing lateral organs is more limited [2]. Gibberellins and brassinosteroids can promote cell expansion, ethylene and jasmonic acid inhibit organ growth by affecting cell expansion [4,5]. A specific isoform of the basic helix-loop-helix transcription factor BIGPETALp (BPEp) limits cell expansion and final petal size, acting downstream of jasmonic acid and in concert with the auxin response factor ARF8 [12,13,14]

Methods

Results

Discussion

Conclusion