Comparative Proteomic Analysis of Self-Compatible Turnera Mutants Suggests Glutathione S-Transferase 8 Is Involved in Overcoming S-Morph Female Self-Incompatibility Response.

Abstract

Distyly is a reproductive system, characterized by the presence of two floral morphs, which promotes outcrossing via physical and biochemical means. In distylous Turnera, the mating type of the S-morph is determined by two genes: YUC6 (male) and BAHD (female). Despite the importance of these S-genes, it is likely that additional genes are involved in the distylous syndrome. Here, we use comparative mass spectrometry analysis to identify differentially expressed proteins in a series of self-compatible mutants and wildtype distylous members of Turnera. Our analysis identified a member of the Glutathione S-transferase family that overwhelmingly correlated with L-morph male mating type. Exploration of the large datasets and previously published work led to the proposal that differential ROS levels in the pistil may contribute towards the self-incompatibility response. To support this hypothesis, we generated a co-expression network for whole flower buds from self-compatible and WT Turnera joelii. This network led to the identification of a series of ROS and auxin-related genes that correlated with self-compatibility. We update previously proposed SI response models to reflect how ROS, jasmonic acid, and brassinosteroid signaling likely establish the S-morph female self-incompatibility response. Overall, this work has identified genes potentially related to self-compatibility and has provided a foundation for future empirical work investigating the basis of the SI response in Turnera.