Silencing of meiosis-critical genes for engineering male sterility in plants

Authors: WANG, XIPING - Northwest Agricultural & Forestry University; SINGER, STACY - University Of Regina; Liu, Zongrang

Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2011
Publication Date: 1/10/2012
Citation: Wang, X., Singer, S.D., Liu, Z. 2012. Silencing of meiosis-critical genes for engineering male sterility in plants. Plant Cell Reports. 31:747-756.

Interpretive Summary: Transgene flow poses a potential risk for the creation of unwanted super or invasive weeds. One of the most effective ways to control gene flow is to incorporate sterility into transgenic plants so that seed-, fruit- and pollen-mediated gene transfer can be completely prevented. In this study, we demonstrated a new environment-friendly strategy for engineering sterility in plants. We found that down-regulation of genes that regulate plant gamete formation can result in sterile plants without compromising plant growth and development. The engineered sterility will be useful for contain transgene flow in crops.

Technical Abstract: Engineering sterile traits in plants through the tissue-specific expression of a cytotoxic gene provides an effective way for containing transgene flow; however, the microbial origin of cytotoxic genes has raised concerns. In an attempt to develop a safe alternative, we have chosen the meiosis-critical genes AHP2, RAD51C and SWITCH1 (SWI) as silencing targets for testing the feasibility of engineering sterility in plants using RNAi. Our results demonstrated that silencing of each of the three genes via hairpin RNA constructs driven by the CaMV35S promoter (termed AHPi, RAD51Ci and SWIi lines) yielded a proportion of lines bearing a very similar partially sterile phenotype in which less than 50% of pollen was viable. In addition, a completely sterile phenotype was also found in RAD51Ci and SWIi lines, but not in the AHPi population. Plants with this sterile phenotype either produced normal-looking but non-viable pollen in the case of RAD51Ci lines or displayed a complete absence of pollen in the case of SWIi lines, which suggests that RAD51C and SWI function at early but distinct stages of meiosis. An analysis of the sterile phenotype in SWI-silenced lines indicated that the level of SWI-specific siRNA did not vary in leaf or floral tissues on the basis of whether the line displayed a fertile or sterile phenotype. Instead, sterility was found to be closely related to a substantial reduction in the level of targeted gene transcript in floral tissues. The sterile phenotype observed in silenced lines was further examined through the use of reciprocal crosses, where only female gametes were found to be capable of fertilization when crossed with wt plants. This work demonstrates that generating sterility through the silencing of key genes involved in the regulation of meiosis is indeed feasible and its advantages and potential applications for transgene containment are discussed.