Compartmentalization of S-RNase and HT-B degradation in self-incompatible Nicotiana.
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.
CIQUIBIC, Departamento de Quimica Biologica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba, Argentina.
Ariel
A
Goldraij
Katsuhiko
K
Kondo
Christopher B
CB
Lee
C Nathan
CN
Hancock
Mayandi
M
Sivaguru
Sonia
S
Vazquez-Santana
Sunran
S
Kim
Thomas E
TE
Phillips
Felipe
F
Cruz-Garcia
Bruce
B
McClure
D000906:Antibodies / Q000032:analysis / Q000276:immunology; D001685:Biological Factors / Q000378:metabolism; D004795:Enzyme Stability; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism; D006239:Haplotypes; D007178:Inbreeding; D008954:Models, Biological; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism; D011058:Pollen / Q000235:genetics / Q000502:physiology; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D012098:Reproduction / Q000502:physiology; D012260:Ribonucleases / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D013997:Time Factors; D014026:Nicotiana / Q000033:anatomy & histology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000201:enzymology
D000906:Antibodies; D001685:Biological Factors; D006023:Glycoproteins; D010940:Plant Proteins; D012260:Ribonucleases