Compatible pollinations in Solanum chacoense decrease both S-RNase and S-RNase mRNA.
Gametophytic self-incompatibility (GSI) allows plants to block fertilization by haploid pollen whose S-allele constitution matches one of the two S-alleles in the diploid styles. GSI in Solanum chacoense requires a stylar S-RNase, first secreted from cells of the transmitting tract then imported into incompatible (self) pollen tubes. However, the molecular mechanisms allowing compatible pollen to evade S-RNase attack are less clear, as compatible pollen tubes also import S-RNase. Using styles of the same age and size in order to lower the degree of inter-style variability in S-RNase levels, we observe reduction of up to 30% of the total non-self stylar S-RNase in vivo during compatible crosses, whereas no degradation of self S-RNases is detected. This marked difference in stylar S-RNase levels dovetails with measurements of pollen-specific Lat52 mRNA, which decreases four-fold in incompatible compared to compatible crosses. Unexpectedly, we also find evidence for a reciprocal signaling mechanism from compatible pollen to the cells of the transmitting tract that results in a roughly three-fold decrease in S-RNase transcript levels. These findings reveal a previously unsuspected feedback loop that may help reinforce the compatible reaction.
Liu
Bolin
B
Institut de Recherche en Biologie Végétale (IRBV), Biology Department, University of Montreal, Montreal, Québec, Canada.
Morse
David
D
Cappadocia
Mario
M
D000483:Alleles; D003433:Crosses, Genetic; D004171:Diploidy; D014644:Genetic Variation; D005838:Genotype; D010944:Plants / Q000235:genetics; D011003:Ploidies; D011058:Pollen / Q000737:chemistry* / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D054817:Pollination; D012333:RNA, Messenger / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry*; D032322:Solanum / Q000201:enzymology / Q000235:genetics*
D012333:RNA, Messenger; D012260:Ribonucleases; C022542:ribonuclease S