Abstract
Self-incompatibility(SI)is an intraspecific re-productive barrier widely present in angiosperms.The SI system with the broadest occurrence in angiosperms is based on an S-RNase linked to a cluster of multiple S-locus F-box(SLF)genes found in the Solanaceae,Plantaginaceae,Rosaceae,and Rutaceae.Recent studies reveal that non-self S-RNase is degraded by the Skip Cullin F-box(SCF)SLF-mediated ubiquitin-proteasome system in a collaborative manner in Petunia,but how self-RNase functions largely remains mysterious.Here,we show that S-RNases form S-RNase con-densates(SRCs)in the self-pollen tube cytoplasm through phase separation and the disruption of SRC formation breaks SI in self-incompatible Petunia hybrida.We further find that the pistil SI factors of a small asparagine-rich protein HT-B and thioredoxin h together with a reduced state of the pollen tube all promote the expansion of SRCs,which then sequester several actin-binding pro-teins,including the actin polymerization factor PhABRACL,the actin polymerization activity of which is reduced by S-RNase in vitro.Meanwhile,we find that S-RNase variants lacking con-densation ability fail to recruit PhABRACL and are unable to induce actin foci formation required for pollen tube growth inhibition.Taken together,our results demonstrate that phase separation of S-RNase promotes SI response in P.hybrida,revealing a new mode of S-RNase action.
基金项目
National Natural Science Foundation of China(32030007)
Strategic Priority Research Program of the Chinese Academy of Sciences(XDB27010302)
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