Gene Expression in Wheat Induced by Inoculation with Puccinia striiformis West

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease of wheat (Triticum aestivum L.) worldwide. A suppression subtractive hybridization (SSH) cDNA library was constructed from Pst-infected seedling leaves of an immune resistant germplasm Shaanmai 139. A total of 84 expressed sequence tags with high quality were obtained and alignment of the sequences identified in 56 Unigenes. Blast EST analysis of these Pst-induced genes showed that they were mostly homologous to genes that are induced by cold or heat stress. BlastX searches identified 45 of the Unigenes as similar to those encoding proteins of known function (e value < 1.00E-5), and eight of unknown function. The genes of known function include those with potential biological roles in signal transmission, energy and metabolism, transcription regulation, phenylpropanoid pathway, and defense response. Semi-quantitative reverse transcription-polymerase chain reaction studies confirmed that some of the cDNAs genes were differentially expressed in Pst-infected plants, with 24 and 72 hpi as the two critical time points for the induction of these genes by inoculation with P. striiformis West race CY32 in wheat. Bimodal patterns were presented in Pst-induced genes, such as senescence-associated genes, omega-6 fatty acid desaturase, and acyl-CoA synthetase. This suggests complex patterns of defense-related gene expression in multi-resistance gene cultivars in response to stripe rust infection.