Trans-Repression of Gene Activity Upstream of T-DNA Tagged RLK902 Links Arabidopsis Root Growth Inhibition and Downy Mildew Resistance

Colette A Ten Hove,Mark De Jong,Dmitry Lapin,Guido Van Den Ackerveken,Renze Heidstra,Annemiek Andel,Yoshihito Suzuki,Yoshiaki Tarutani,Gabino F Sanchez-Perez,Edward Newbigin

doi:10.1371/journal.pone.0019028

Abstract

Receptor-like kinases (RLKs) constitute a large family of signal perception molecules in Arabidopsis. The largest group of RLKs is the leucine-rich repeat (LRR) class that has been described to function in development and defense. Of these, CLAVATA1 (CLV1) and ERECTA (ER) receptors function in maintaining shoot meristem homeostasis and organ growth, but LRR RLKs with similar function in the root remain unknown. For the interaction of Arabidopsis with the oomycete pathogen Hyaloperonospora arabidopsidis the involvement of LRR RLKs has not been demonstrated. A set of homozygous T-DNA insertion lines mutated in LRR RLKs was investigated to assess the potential role of these receptors in root meristem maintenance and compatibility. One mutant line, rlk902, was discovered that showed both reduced root growth and resistance to downy mildew in a recessive manner. The phenotypes of this mutated line could not be rescued by complementation, but are nevertheless linked to the T-DNA insertion. Microarray studies showed that gene expression spanning a region of approximately 84 kb upstream of the mutated gene was downregulated. The results suggest T-DNA mediated trans-repression of multiple genes upstream of the RLK902 locus links both phenotypes.

Highlights

Plants continuously form new organs during their entire lifecycle
To investigate the function of leucine-rich repeat (LRR) Receptor-like kinases (RLKs) in root development we screened a collection of 69 homozygous T-DNA insertion mutants
The activation tag T-DNA in rlk902 is inserted at the end of the single intron of RLK902 disrupting its expression

Summary

Introduction

Plants continuously form new organs during their entire lifecycle. These organs are derived from two main populations of stem cells located in the meristems in the shoot and root apices. The shoot apical meristem produces all the aboveground organs and tissues of the plant, i.e. the stems, leaves and flowers, whereas the root meristem gives rise to the entire root system. Meristems must maintain a strict regulation of stem cell maintenance, cell division and cell differentiation. In the heart of the shoot meristem a feedback loop involving the LRR RLK signaling ensures the integrity and size of the stem cell pool (reviewed by [1]). LRR RLK members involved in root meristem maintenance remain elusive

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Conclusion