Genetically Engineering Photoperiod-Sensitive Male Sterile Rice Through Antisense-OsPDCD5 Gene

Programmed cell death (PCD) is a crucial process for plants during development and stress survival. Here we reported that down-regulation of the OsPDCD5 gene by antisense technology could induce pollen sterility in photoperiod-sensitive rice Zhonghua11. The male sterility of transgenic rice is reversible, determined by photoperiod. The antisense-OsPDCD5 transgenic plants demonstrate aborted pollens during pollen development under natural long-day conditions (above 13.5 h of light), accompanied by obviously postponed heading time. They can gradually restore fertility and reduce the length of the growing period, accompanied with the reduction of sunlight time (during 12.8h-13 h of light). Photoperiod-sensitive transgenic rice could get 70%-80% pollen fertile rate and reach similar seed-setting rate compared with the control when grow under 11h-12 h of light, with no postponed heading time. RNA in situ hybridization studies showed that antisense-OsPDCD5 was expressed in various tissues of transgenic rice and endogenous OsPDCD5 was reduced compared with control rice. Data from real-time quantitative PCR also confirmed that the level of OsPDCD5 mRNA in Zhonghua11 was affected by photoperiod and the amounts of OsPDCD5 mRNA in transgenic rice were obviously reduced under different environments. Analysis of tissue sections of anthers at different developmental stages displayed that four layers of anther wall cells retarded their degradation compared with the control under natural long-day photoperiod (above 13.5 h of light), especially the tapetum cells. The TUNEL test also confirmed that tapetum cells retarded its PCD process in male sterile transgenic plants. In F1 hybrids from transgenic plants and rice varieties antisense-OsPDCD5 gene dosage halved, and the expression level of OsPDCD5 increased slightly compared with the female parent but still lower than male parent. As a result most pollen could be fertile and the F1 hybrids could get normal seed set rates under long day conditions (above 13.5 h of light). This photosensitive male sterility (PGMS) line produced by the expression of antisense-OsPDCD5 could be applied in production of hybrid rice using two-line breeding system. This environmentally-friendly breeding technology is easy to implement and control, and shorts the breeding period. It has great advantages for commercial application.