The cleistogamy of the superwoman1-cleistogamy1 mutation is sensitive to low temperatures during the lodicule-forming stage

We reported previously that the rice (Oryza sativa L.) cleistogamous mutation superwoman1-cleistogamy1 (spw1-cls1) was applicable to inhibit outcrossing between genetically modified varieties and their relatives, which causes pollen-mediated gene flow or disturbance of line purity. The cleistogamy of spw1-cls1 is caused by decreased protein-protein interactions between the mutant SPW1 and its partner proteins. Importantly, these interactions are restored under low-temperature conditions, but whether the cleistogamy of spw1-cls1 is affected by this phenomenon was unclear. In this study, we cultivated spw1-cls1 in various regions of Japan and confirmed that its flowers opened at low temperatures. Moreover, we compared the morphology of a series of lodicules generated at various temperatures. The results indicated that the cleistogamy of spw1-cls1 is thermosensitive and is gradually disturbed as the temperature decreases. This was correlated with the protein interaction pattern of the mutant SPW1 as reported previously. Then, we revealed the critical period for the low-temperature-induced instability of the phenotype of spw1-cls1 and examined the effect of daily temperature changes on cleistogamy. The results may facilitate simulation of the phenotype of spw1-cls1 at various temperatures and the prediction of regions where the cleistogamy of spw1-cls1 can be stably used to inhibit outcrossing.