Genetic analysis of mechanisms linking cell wall integrity with growth control in Arabidopsis

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office

Abstract

We propose to identify genes in a putative signalling pathway that links changes in cell wall composition to sugar response pathways that control growth, development and storage processes. We have characterised a gene called HSR8 in a genetic screen for sugar-responsive growth and development in Arabidopsis. HSR8 is allelic to MUR4, which catalyses arabinose formation in the Golgi compartment where it is destined for cell wall polysaccharide biosynthesis. hsr8 mutations are suppressed by prl1, a mutation affecting sugar and hormonal- responsive signalling and gene expression. This suggests that cell wall changes caused by hsr8 and two other cell wall biosynthetic mutants, mur1-1 and mur3-1, are signalled to increase sugar-dependent growth and development via PRL1. We showed that treatment of seedlings with low levels of borate reverses the growth and developmental phenotypes in these three mutants. Borate acts in the cell wall to cross link polysaccharides such as RG II and pectins. Altered cell wall polysaccharide composition weakens these cross links and high borate levels can reverse this. The sugar-dependent growth and developmental phenotypes observed in the hsr8 and other mutants are robust and quantitative and will be used in a genetic screen to identify new components in this pathway and characterise their function. We will also establish genetic interactions with known sugar signalling pathways to build up a more integrated view of how cell wall changes are sensed and signalled to the cell, for example to sugar-response pathways that regulate growth and resource allocation. In the long term we aim to establish sufficient knowledge about cell wall signalling pathways and resource allocation to help to manipulate cell wall synthesis in bioenergy crops- for example by manipulating carbohydrate incorporation into cell wall synthesis.

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