Drought-induced differences in gene expression in parental and hybrid plants of the Piriqueta caroliniana complex

The phenotypic changes that organisms exhibit in response to varying environmental conditions are mediated by changes in gene expression.  A soybean microarray of 9000 unigene probes was used to screen gene transcript expression in replicated plant genotypes within the Piriqueta caroliniana complex, which consists of parental morphotypes (caroliniana and viridis) and advanced-generation hybrid derivatives, in drought and control conditions.  Transcripts strongly associated with drought response were identified with ANOVA, testing for significance over variation in biological replication and accounting for multiple significance tests.  We found that hybrids have more genes that are differentially expressed in drought (57 genes), compared to the caroliniana (33 genes) and viridis (32 genes) morphotypes.  The expression profile of drought response in hybrids was found to be more highly correlated with caroliniana than with viridis.  This is not surprising, due to observed higher survival of caroliniana and hybrids in drought conditions compared to viridis.  Additionally, a high level of novel drought response was found in hybrids- 39% of significant genes were not differentially expressed in either of the parentals, with caroliniana (6%) and viridis (9%) having substantially fewer unique differentially expressed genes.  Patterns found in classes of genes will be shown using gene ontology groupings.  This study lends insight into the genetics of hybridization and the potential response of hybrid species to changing environmental conditions.