Characterisation and expression of Receptor-like Cytoplasmic Kinases in Medicago truncatula during Rhizobial and Arbuscular Mycorrhizal symbioses

Jackson, Kirsty (2015) Characterisation and expression of Receptor-like Cytoplasmic Kinases in Medicago truncatula during Rhizobial and Arbuscular Mycorrhizal symbioses. Doctoral thesis, University of East Anglia.

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Abstract

Legume plants have evolved the ability to form a mutualistic symbiosis with nitrogen-fixing bacteria known as rhizobia. Studies using mutant Medicago truncatula and Lotus japonicus have identified many genes that are necessary for this mutualism. Some of these genes have also been shown to be necessary for symbiosis with arbuscular mycorrhiza fungi (AMF). These common genes make up part of a signalling pathway known as the common symbiosis pathway (CSP) which serves to prepare the plant for the entry of the symbiont into the root. Although the core members of this signalling pathway are known there are still large gaps, and many of the genes involved in the infection process haven’t yet been identified. Using the Medicago Gene Expression Atlas (MtGEA) and in-house gene expression data three family Receptor-like Cytoplasmic Kinase (RLCK) genes were identified in M. truncatula which were differentially regulated during rhizobial and AMF colonisation. Analysis of Tnt1 insertion mutants for the one of these genes, named RLCK3 due to similarity to the rice gene family RLCK-OS3, revealed an apparently novel mycorrhizal phenotype with stunted arbuscule development. However, segregation analysis showed the phenotype was not linked to RLCK3; as such the locus was named SCOOBY. The other genes identified were similar to the rice gene family RLCK-XV and so named RLCK1 and RLCK2. Both RLCK1 and RLCK2 encode soluble RD kinases with high homology to each other. Promoter-GUS analysis showed RLCK1 and RLCK2 expression associated with entry and accommodation of the symbionts. rlck1 and rlck2 mutants had a low level of arbusculation and misshaped arbuscules. rlck1 was hyperinfected by rhizobia and had a significant reduction in nodule number. RNAi knockdown of rlck1/rlck2 had a significantly reduced nodule number compared to the empty vector control. RLCK1 and RLCK2 possibly have partially redundant or synergistic roles during rhizobial and arbuscular mycorrhizal symbioses.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Stacey Armes
Date Deposited:	09 Sep 2015 14:35
Last Modified:	09 Sep 2015 14:35
URI:	https://ueaeprints.uea.ac.uk/id/eprint/54314
DOI:

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