Expression analysis of Clavata1-like and Nodulin21-like genes from Pinus sylvestris during ectomycorrhiza formation

The ecology and physiology of ectomycorrhizal (EcM) symbiosis with conifer trees are well documented. In comparison, however, very little is known about the molecular regulation of these associations. In an earlier study, we identified three EcM-regulated Pinus expressed sequence tags (EST), two of which were identified as homologous to the Medicago truncatula nodulin MtN21. The third EST was a homologue to the receptor-like kinase Clavata1. We have characterized the expression patterns of these genes and of auxin- and mycorrhiza-regulated genes after induction with indole-3-butyric acid in Pinus sylvestris and in a time course experiment during ectomycorrhizal initiation with the co-inoculation of 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Our results suggest that different P. sylvestris nodulin homologues are associated with diverse processes in the root. The results also suggest a potential role of the Clv1-like gene in lateral root initiation by the ectomycorrhizal fungus

Characterization of an Aux/IAA cDNA upregulated in Pinus pinaster roots in response to colonization by the ectomycorrhizal fungus Hebeloma cylindrosporum.

In an attempt to determine whether fungal auxin affects host plant gene expression during mycorrhizal formation, an auxin upregulated cDNA, Pp-iaa88, was isolated by differential screening of a cDNA library made from auxin-treated Pinus pinaster roots.Pp-iaa88 codes for a polypeptide that shares extensive homology to auxin-inducible Aux/IAA proteins, which are supposed to act as transcription factors. Cycloheximide did not inhibit auxin-induced mRNA accumulation, indicating that Pp-iaa88 upregulation is a primary (direct) auxin response.The level of Pp-iaa88 transcripts in roots increased following inoculation with either an indoleacetic acid-overproducing mutant or a wild-type strain of the ectomycorrhizal fungus Hebeloma cylindrosporum. With both strains, mRNA accumulation was detectable as soon as fungal hyphae reached the root and it increased during differentiation of symbiotic structures. The kinetics of Pp-iaa88 transcript accumulation was closely connected with the dynamics of symbiosis establishment and was more rapid with the mutant than with the wild-type strain.As a putative transcription factor expressed at the very early stages of symbiosis establishment, Pp-iaa88 could play a key role in mycorrhizal formation

Characterization of a Pinus pinaster cDNA encoding an auxin up-regulated putative peroxidase in roots

International audienc

Characterization of a Pinus pinaster cDNA encoding an auxin up-regulated putative peroxidase in roots

International audienc