Compartmentalization of S-RNase and HT-B degradation in self-incompatible Nicotiana

• Published in: Nature 2006-02, Vol.439 (7078), p.805-810
• Main Authors: Goldraij, A, Kondo, K, Lee, C.B, Hancock, C.N, Sivaguru, M, Vazquez-Santana, S, Kim, S, Phillips, T.E, Cruz-Garcia, F, McClure, B
• Format: Article
• Language: English
• Subjects: Antibodies - analysis; Antibodies - immunology; Biological and medical sciences; Biological Factors - metabolism; Cytotoxicity; Enzyme Stability; Fundamental and applied biological sciences. Psychology; Genes; Glycoproteins; Glycoproteins - chemistry; Glycoproteins - metabolism; gynoecium; Haplotypes; Humanities and Social Sciences; Inbreeding; Models, Biological; multidisciplinary; Mutation; Nicotiana; Nicotiana - anatomy & histology; Nicotiana - enzymology; Nicotiana - genetics; Nicotiana - physiology; Nicotiana alata; Plant breeding; plant fertility; Plant physiology and development; plant proteins; Plant Proteins - immunology; Plant Proteins - metabolism; Pollen; Pollen - genetics; Pollen - physiology; pollen rejection; pollen tubes; pollination; protein degradation; Protein Processing, Post-Translational; Protein Transport; Proteins; Reproduction - physiology; ribonucleases; Ribonucleases - metabolism; Science; Science (multidisciplinary); selfing; Sexual reproduction; Species Specificity; styles; Substrate Specificity; Time Factors; vacuoles; Vacuoles - enzymology; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature04491

Pollen-pistil interactions are crucial for controlling plant mating. For example, S-RNase-based self-incompatibility prevents inbreeding in diverse angiosperm species. S-RNases are thought to function as specific cytotoxins that inhibit pollen that has an S-haplotype that matches one of those in the pistil. Thus, pollen and pistil factors interact to prevent mating between closely related individuals. Other pistil factors, such as HT-B, 4936-factor and the 120 kDa glycoprotein, are also required for pollen rejection but do not contribute to S-haplotype-specificity per se. Here we show that S-RNase is taken up and sorted to a vacuolar compartment in the pollen tubes. Antibodies to the 120 kDa glycoprotein label the compartment membrane. When the pistil does not express HT-B or 4936-factor, S-RNase remains sequestered, unable to cause rejection. Similarly, in wild-type pistils, compatible pollen tubes degrade HT-B and sequester S-RNase. We suggest that S-RNase trafficking and the stability of HT-B are central to S-specific pollen rejection.