OsPIF14 gene knockout delays seed germination, seedling development and grain filling in rice

Abstract

Phytochrome-Interacting Factors (PIFs) are transcription factors belonging to the basic helix-loop-helix (bHLH) family that regulate essential metabolic processes in plants. However, the physiological role of these proteins is not fully understood in rice. Therefore, this study aimed to understand the role of PIF14 in the photo- and skotomorphogenesis processes. For this, rice seeds knocked out for the OsPIF14 gene (14-KO1 and 14-KO2 lines) and wild type (WT) were exposed to two growth regimes, 100 mol photons m-2 s-1 and dark, for 16 days in a growth chamber and physiological parameters were assessed. It was observed that the germination rate of both mutants was lower than WT and only this latter showed 100% of germination rate in both growth conditions. The root and shoot length of seeds germinated under light were around two times less in the mutants when compared to WT. A similar result was observed in seeds germinated in the dark. However, this response was more prominent in the roots length. The content of chlorophyll a, b and carotenoids of the transformed light-grown seedlings was lower compared to WT. While in the dark-grown seedlings, only the content of chlorophyll a and b was lower than WT. The chlorophyll a/b ratio showed no difference in light-grown genotypes. However, in the dark-grown mutants, the chlorophyll a/b ratio was higher than WT. The size and length of seeds with shell was lower in the transformed lines when compared to WT seeds. Shelled seeds showed only a trend of lesser value in these parameters. The starch content was lower, while the concentration of total soluble sugars and sucrose were higher in transformed seeds when compared to WT. These results suggest that the transcription factor PIF14 is related to the processes of germination, growth, photosynthetic pigments synthesis/accumulation and carbohydrates content in rice. In addition, the altered carbohydrate content affected germination rate and, consequently, the subsequent developmental processes. Thus, this transcription factor plays an important role in the processes of morphogenesis in rice.