Pollen-pistil Interactions in the Genus Nicotiana

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

The goal of this project is to identify and characterize factors that contribute to S-allele-specific pollen recognition in Nicotiana alata. In this species, the S-locus controls intraspecific compatibility. Pollen is rejected when the S-allele in the pollen is the same as one of the S-alleles expressed in the pistil. S-RNases control the specificity of pollen rejection, but other factors contribute to S-allele-specific pollen recognition in other ways. Our main objective is to identify and characterize these non-S-RNase factors. HT-protein is one such factor that appears to be an unstable component of the stylar extracellular matrix. Antisense suppression of HT prevents S-allele-specific pollen rejection, but its precise function is unknown. We propose experiments to determine the abundance of HT-protein during style development, and why it is so unstable. We have found that two specific stylar proteins bind to S-RNase in vitro. One is a previously characterized protein, NaTTS, that is implicated in growth of compatible pollen tubes. The second, designated p11, has not been well characterized. NaTTS and p11 are putative non-S-RNase factors that may be implicated in both pollen rejection and in supporting compatible pollen tube growth. Gel filtration and protein blot analysis are proposed to determine the molecular weight and composition of NaTTS/S-RNase/p11 complexes. NaTTS and p11 will be also expressed in bacteria and then used to test for interactions in vitro. Antisense methods will be used to determine whether p11 affects compatible or incompatible pollinations in vivo. To identify new non-S-RNase factors, we have generated populations that segregate for the ability to perform S-allele-specific pollen rejection. cDNA AFLP will be used to screen for new sequences associated with pollen rejection phenotype. The impact of this research will be to provide a better understanding of the genetic mechanisms for pollen recognition and rejection. This is of practical significance to biotechnologists who wish to manipulate plant breeding behavior.