The RNA Polymerase-Associated Factor 1 Complex Is Required for Plant Touch Responses.

Gregory S Jensen,Kateryna Fal,Elizabeth S Haswell,Olivier Hamant

doi:10.1093/jxb/erw439

Abstract

Thigmomorphogenesis is a stereotypical developmental alteration in the plant body plan that can be induced by repeatedly touching plant organs. To unravel how plants sense and record multiple touch stimuli we performed a novel forward genetic screen based on the development of a shorter stem in response to repetitive touch. The touch insensitive (ths1) mutant identified in this screen is defective in some aspects of shoot and root thigmomorphogenesis. The ths1 mutant is an intermediate loss-of-function allele of VERNALIZATION INDEPENDENCE 3 (VIP3), a previously characterized gene whose product is part of the RNA polymerase II-associated factor 1 (Paf1) complex. The Paf1 complex is found in yeast, plants and animals, and has been implicated in histone modification and RNA processing. Several components of the Paf1 complex are required for reduced stem height in response to touch and normal root slanting and coiling responses. Global levels of histone H3K36 trimethylation are reduced in VIP3 mutants. In addition, THS1/VIP3 is required for wild type histone H3K36 trimethylation at the TOUCH3 (TCH3) and TOUCH4 (TCH4) loci and for rapid touch-induced upregulation of TCH3 and TCH4 transcripts. Thus, an evolutionarily conserved chromatin-modifying complex is required for both short- and long-term responses to mechanical stimulation, providing insight into how plants record mechanical signals for thigmomorphogenesis.

Highlights

It is firmly established that development in multicellular organisms relies on the local concentration of key biochemical signals such as hormones or growth factors (Wolpert, 1969)
We show here that the Arabidopsis polymerase II-associated factor 1 (Paf1) complex is a critical factor for stem and root thigmomorphogenesis, stereotypical alterations in plant form that are made in response to repeated mechanical disturbance
We show that THS1/VERNALIZATION INDEPENDENCE 3 (VIP3) is required for both global and genic levels of H3K36 methylation and for upregulation of two canonical touch-inducible loci in response to touch stimulation

Summary

Introduction

It is firmly established that development in multicellular organisms relies on the local concentration of key biochemical signals such as hormones or growth factors (Wolpert, 1969). We begin to address the genetic pathways by which a repeated mechanical stimulus leads to a developmental change during plant thigmomorphogenesis, a stereotypical developmental alteration in the plant body plan that can be induced by shaking, rubbing, bending, or brushing leaves or stems (Chehab et al, 2009; Coutand, 2010). Repeated mechanical stimulation can result in a more flexible stem and an increase in root mass relative to the shoot Taken together, these morphological changes are thought to produce a body plan that is more resistant to damage upon future mechanical challenges. These morphological changes are thought to produce a body plan that is more resistant to damage upon future mechanical challenges This presents an intriguing conversion of energy from an elastic deformation (i.e. bending) into a developmental response (i.e. growth)

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Conclusion