A time course of GFP expression and mRNA stability in pollen tubes following compatible and incompatible pollinations in Solanum chacoense.
The self-incompatibility (SI) reaction in the Solanaceae involves molecular recognition of stylar haplotypes by pollen and is mediated by the S-locus from which a stylar-localized S-RNase and several pollen-localized F-box proteins are expressed. S-RNase activity has been previously shown to be essential for the SI reaction, leading to the hypothesis that pollen rejection in incompatible crosses is due to degradation of pollen RNA. We used pollen expressing the fluorescent marker GFP, driven by the LAT52 promoter, to monitor the accumulation of mRNA and protein in pollen after compatible and incompatible pollinations. We find that GFP mRNA and protein gradually accumulate in pollen tubes until at least 18-h post-pollination and, up to this time, are only slightly more abundant in compatible compared with incompatible crosses. However, between 18- and 24-h post-pollination, pollen tube GFP mRNA and protein levels show a dramatic increase in compatible crosses and either remain constant or decrease in incompatible crosses. In contrast to these molecular correlates, the growth rates of compatible and incompatible pollen tubes begin to differ after 6-h post-pollination. We interpret the changes in growth rate at 6-h post-pollination as the previously described transition from autotrophic to heterotrophic growth. Thus, while pollen rejection is generally considered to result from the cytotoxic effects of S-RNase activity, this time course reveals that a difference in the growth rate of compatible and incompatible pollen appears prior to any marked effects on at least some types of pollen RNA.
Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke est, Montreal, QC H1X 2B2, Canada.
Bolin
B
Liu
Nicolas
N
Boivin
David
D
Morse
Mario
M
Cappadocia
D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D053205:Pollen Tube / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D054817:Pollination; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012260:Ribonucleases / Q000235:genetics / Q000378:metabolism; D060436:Self-Incompatibility in Flowering Plants / Q000235:genetics*; D032322:Solanum / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D013997:Time Factors
D010940:Plant Proteins; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins; D012260:Ribonucleases; C022542:ribonuclease S