|Medeiros, Flavio h. v.|
|Souza, Ricardo m.|
|Medeiros, Fernanda c.l.|
|Ferro, Henrique m.|
Submitted to: Plant and Soil
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2011
Publication Date: 10/1/2011
Citation: Medeiros, F., Souza, R., Medeiros, F., Zhang, H., Wheeler, T., Payton, P.R., Ferro, H., Pare', P.W. 2011. Transcriptional Profiling in Cotton Associated with Bacillus Subtilis (UFLA285) Induced Biotic-stress Tolerance. Plant and Soil. 347(1-2):327-337. Interpretive Summary: For crops such as cotton that are often grown for several years without rotation, soil pathogens are a persistent threat to productivity across the globe. The cotton pathogen Rhizoctonia solani is able to overwinter as dormant sclerotia, clamidospores, or in a saprophytic form and can cause substantial harvest losses as soil-pathogen titers increase. Such a plant pathogen interferes with xylem flow, simulates water-stress conditions, and result in greater plant susceptibility to drought or salt stress. While sustained efforts have been underway to breed for abiotic stress tolerance in cotton, few programs have targeted soil-borne pathogen resistance. Soil microbes also result in positive effects on plant growth and can be utilized as anti-biosis agents against pathogens, induce endogenous plant defense responses, or promote plant growth in a wide range of agricultural crops. Model systems have been employed to unravel mechanisms of plant inducible biotic and abiotic stress-tolerance activated by plant growth promoting rhizobacteria (PGPR). In Arabidopsis, PGPR have been shown to suppress Psuedomonas syringae infection and exposure to Bacillus subtilis has been shown to increase salt tolerance. This study examines the effects of B. subtilis exposure on cotton growth, response to pathogenic R. solani, and gene transcription. We identified 247 genes differentially regulated in response to B. subtilis exposure including disease resistance proteins, drought/salt reponse genes, and genes for osmotic adjustment. Additionally, there was an increase in root growth and enhanced resistance to damping off caused by R. solani infection. For the first time, PGPR treatment resulting in cotton protection against a soil-borne pathogen has been proposed. Future experiments will verify the role of drought tolerance in the disease protection and enzyme activity as well as physical barriers predicted to be operative form the microarray data. It is expected that Bacillus subtilis UFLA285 will provide cotton growers with a new, environmentally innocuous, biological agent allowing for improved plant protection against biotic- and abiotic-stress and in turn, superior crop performance.
Technical Abstract: Plant growth promoting rhizobacteria (PGPR) confer disease resistance in many agricultural crops. In the case of Bacillus subtilis (UFLA285) isolated from the cotton producing state of Mato Grosso (Brazil), in addition to inducing foliar and root growth, disease resistance against damping-off caused by Rhizoctonia solani is observed. To probe molecular responses activated by the cotton growth promoting strain UFLA285, transcriptional analyses were performed in infected cotton with and without UFLA285-seed treatment. Microarray data of stem tissue revealed 247 genes differentially regulated in infected plants, seed treated versus untreated with UFLA285. Transcripts encoding disease resistance proteins via jasmonate/ethylene signaling as well as osmotic regulation via proline synthesis genes were differentially expressed with UFLA285 induction. Consistent with transcriptional regulation, UFLA285 increased plant-proline accumulation and dry weight. This study has identified transcriptional changes in cotton, induced by the beneficial soil bacterium UFLA285 and associated with disease control.