Overexpression of EgROP1, a Eucalyptus vascular-expressed Rac-like small GTPase, affects secondary xylem formation in Arabidopsis thaliana

• Published in: The New phytologist Vol. 183; no. 4; pp. 1014 - 1029
• Main Authors: Foucart, Camille, Jauneau, Alain, Gion, Jean-Marc, Amelot, Nicolas, Martinez, Yves, Panegos, Patricia, Grima-Pettenati, Jacqueline, Sivadon, Pierre
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-01-2009; Blackwell Publishing; Blackwell Publishing Ltd; Wiley
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis thaliana; Biochemistry, Molecular Biology; cell expansion; Cell walls; Chromosome Mapping; DNA, Complementary; Epidermal cells; Eucalyptus; Eucalyptus - genetics; Eucalyptus - growth & development; Fiber cells; Gene Library; Genes, Plant; Genomics; GTP Phosphohydrolases - genetics; Leaves; Life Sciences; lignification; Lignin; Monomeric GTP-Binding Proteins - genetics; Plant cells; Plant Leaves - genetics; Plant Leaves - growth & development; Plants; Plants, Genetically Modified; Polymorphism, Genetic; Quantitative Trait Loci; Rac-like ROP; Reverse Transcriptase Polymerase Chain Reaction; secondary cell wall; Secondary xylem; Transgenic plants; Trees - genetics; wood quality; Xylem; Xylem - genetics; Xylem - growth & development
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2009.02910.x

To better understand the genetic control of secondary xylem formation in trees we analysed genes expressed during Eucalyptus xylem development. Using eucalyptus xylem cDNA libraries, we identified EgROP1, a member of the plant ROP family of Rho-like GTPases. These signalling proteins are central regulators of many important processes in plants, but information on their role in xylogenesis is scarce. Quantitative real-time reverse-transcriptase polymerase chain reaction (qRT-PCR) confirmed that EgROP1 was preferentially expressed in the cambial zone and differentiating xylem in eucalyptus. Genetic mapping performed in a eucalyptus breeding population established a link between EgROP1 sequence polymorphisms and quantitative trait loci (QTLs) related to lignin profiles and fibre morphology. Overexpression of various forms of EgROP1 in Arabidopsis thaliana altered anisotropic cell growth in transgenic leaves, but most importantly affected vessel element and fibre growth in secondary xylem. Patches of fibre-like cells in the secondary xylem of transgenic plants showed changes in secondary cell wall thickness, lignin and xylan composition. These results suggest a role for EgROP1 in fibre cell morphology and secondary cell wall formation making it a good candidate gene for marker-based selection of eucalyptus trees.