Dissecting Phaseolus vulgaris innate immune system against Colletotrichum lindemuthianum infection.
BACKGROUND
The genus Colletotrichum is one of the most economically important plant pathogens, causing anthracnose on a wide range of crops including common beans (Phaseolus vulgaris L.). Crop yield can be dramatically decreased depending on the plant cultivar used and the environmental conditions. This study aimed to identify potential genetic components of the bean immune system to provide environmentally friendly control measures against this fungus.


RESULTS
As the common bean is not amenable to reverse genetics to explore functionality and its genome is not fully curated, we used putative Arabidopsis orthologs of bean expressed sequence tag (EST) to perform bioinformatic analysis and experimental validation of gene expression to identify common bean genes regulated during the incompatible interaction with C. lindemuthianum. Similar to model pathosystems, Gene Ontology (GO) analysis indicated that hormone biosynthesis and signaling in common beans seem to be modulated by fungus infection. For instance, cytokinin and ethylene responses were up-regulated and jasmonic acid, gibberellin, and abscisic acid responses were down-regulated, indicating that these hormones may play a central role in this pathosystem. Importantly, we have identified putative bean gene orthologs of Arabidopsis genes involved in the plant immune system. Based on experimental validation of gene expression, we propose that hypersensitive reaction as part of effector-triggered immunity may operate, at least in part, by down-regulating genes, such as FLS2-like and MKK5-like, putative orthologs of the Arabidopsis genes involved in pathogen perception and downstream signaling.


CONCLUSIONS
We have identified specific bean genes and uncovered metabolic processes and pathways that may be involved in the immune response against pathogens. Our transcriptome database is a rich resource for mining novel defense-related genes, which enabled us to develop a model of the molecular components of the bean innate immune system regulated upon pathogen attack.
Department of Biology, University of Texas, Arlington, Texas, United States of America.
Paula Rodrigues
PR
Oblessuc
Aline
A
Borges
Bablu
B
Chowdhury
Danielle Gregório Gomes
DG
Caldas
Siu Mui
SM
Tsai
Luis Eduardo Aranha
LE
Camargo
Maeli
M
Melotto
D000040:Abscisic Acid / Q000378:metabolism; D001483:Base Sequence; D020231:Colletotrichum; D019295:Computational Biology; D003517:Cyclopentanes / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D020224:Expressed Sequence Tags; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D005875:Gibberellins / Q000378:metabolism; D007113:Immunity, Innate / Q000276:immunology*; D018448:Models, Immunological; D008969:Molecular Sequence Data; D054883:Oxylipins / Q000378:metabolism; D027805:Phaseolus / Q000235:genetics*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D059467:Transcriptome / Q000235:genetics
D003517:Cyclopentanes; D003583:Cytokinins; D005030:Ethylenes; D005875:Gibberellins; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid; D000040:Abscisic Acid; C036216:ethylene