Journal of Experimental Botany 63: 6325-6334 (2012)

Role of a respiratory burst oxidase of Lepidium sativum (cress) seedlings in root development and auxin signalling ^[W][OA]

Simon Fraser University, Department of Biological Sciences, 8888 University Drive, Burnaby BC V5A 1S6, Canada (KM, ARK)
University of Freiburg, Faculty of Biology, Institute for Biology II, Botany / Plant Physiology, Schänzlestr. 1, D-79104 Freiburg, German (AL, GLM)
School of Biological Sciences, Plant Molecular Science, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK (GLM); Web: 'The Seed Biology Place' - www.seedbiology.eu
* equal contributions

Received 20 July 2012; Revised 11 September 2012; Accepted 21 September 2012
Advance Acess publication 23 October 2012
DOI 10.1093/jxb/ers284

Abstract
Reactive oxygen species are increasingly perceived as players in plant development and plant hormone signalling pathways. One of these species, superoxide, is produced in the apoplast by respiratory burst oxidase homologues (rbohs), a family of proteins that is conserved throughout the plant kingdom. Because of the availability of mutants, the focus of research into plant rbohs has been on Arabidopsis thaliana, mainly on AtrbohD and AtrbohF. This study investigates: (i) a different member of the Atrboh family, AtrbohB, and (ii) several rbohs from the close relative of A. thaliana, Lepidium sativum ('cress'). Five cress rbohs (Lesarbohs) were sequenced and it was found that their expression patterns were similar to their Arabidopsis orthologues throughout the life cycle. Cress plants in which LesarbohB expression was knocked down showed a strong seedling root phenotype that resembles phenotypes associated with defective auxin-related genes. These transgenic plants further displayed altered expression of auxin marker genes including those encoding the auxin responsive proteins 14 and 5 (IAA14 and IAA5), and LBD16 (LATERAL ORGAN BOUNDARIES DOMAIN16), an auxin-responsive protein implicated in lateral root initiation. It is speculated that ROS produced by rbohs play a role in root development via auxin signalling.

Key words: AtrbohB, auxin, Lepidium sativum, Rboh, reactive oxygen species (ROS), RNAi, root development, superoxide.

Financial support: We gratefully acknowledge funding through a European Commission Marie Curie IOF grant for KM, and from a Natural SCiences and Engineering Research Council of Canada (NSERC) Discovery grant to ARK. The position and research of AL is funded by the Deutsche Forschungsgemeinschaft (Grants DFG LE720/6), which is gratefully acknowledged.