The Xue Lab is investigating the molecular mechanisms of pollen recognition in flowering plants using a combined approach of genetics, genomics, biochemistry and cell biology. Currently, we are focusing on the following areas:
1. Molecular control of self-incompatibility in Antirrhinum
Self-incompatibility (SI) is a widely-distributed genetic mechanism to prevent inbreeding in flowering plants and represents a model system to study molecular basis of pollen recognition and rejection. In solanaceous-type self-incompatible species, recent studies have shown that the S-locus encodes two types of genes in a haplotype manner controlling the pistil and pollen function of SI, respectively. A class of ribonucleases known as S-RNases mediates the pistil function, and a novel F-box gene called S-locus F-box (SLF) controls the pollen function. The first member of the SLF family, AhSLF-S2, was identified in Antirrhinum. We have shown that it mediates the pollen function of S-RNase-based SI and its protein product forms part of an SCF (Skp1/Cullin or CDC53/F-box) complex to target S-RNases for destruction by the ubiquitin/26S proteosome-mediated proteolytic pathway during compatible pollination. However, little is known about how these two proteins interact with each other to elicit SI responses. Currently, we are taking a combination of molecular genetics, biochemistry and cell biology to address this issue in Antirrhinum.
2. Molecular studies on pollination and fertilization in rice
Pollination and fertilization are key steps leading to seed formation. But, relatively little is known about their molecular control in rice. To identify genes involved in these processes, we have constructed a cDNA microarray containing over 10K unique cDNA in rice and monitored gene expression profiles during pollination. Subsequently, over 200 candidate cDNA have been found with possible roles in pollination in rice. We are investigating their detailed functions using a variety of approaches. In addition, we are collaborating with Drs Weiren Wu and Yuanling Duan from Fujian Agricultural University of China to clone several key genes controlling rice reproductive development using a map-based method.
3. Identification of genes controlling cotton fiber formation
Cotton fibers are single cell-derived structures from ovule epidermis. Very little is known about their molecular control. Based on the fact that both trichomes and fibers are derived from single cells, we have identified numerous MYB genes expressed during fiber formation. In particular, one gene known as GhMYB109 is specifically expressed in fiber initials and elongating fibers, suggesting that it likely controls these steps. Currently, we are disecting its function through a transgenic approach.