Abstract
Plant male sterility systems are important tools for breeding F1 hybrid crops as well as for biocontainment of genetically modified (GM) crops and weedy species. Previous methods such as mechanical, chemical, and cytoplasmic sterility as well as recessive nuclear mutations have been utilised with some success, but commonly show incomplete sterility or logistical limitations for use. Restorable genetic male sterility systems allow for fertility to be restored to male-sterile lines for the purpose of seed production. In these systems, a pollen disruptor construct can be used to prevent inheritance of the restorer through the male line. This makes it possible for fertile maintainer lines to produce 50% male-sterile seed. Restorable male sterility systems have been created in rice and maize, however their use of recessive sterility mutations and choice of α-amylase as a pollenlethal mechanism may not provide complete sterility, and makes them unsuitable for use in many species.
This research tested genetic components for use in a novel dominant restorable male sterility (DRMS) system, which aims to provide complete male sterility for use in a wide range of crop species. Tested components included dominant male sterility constructs to cause reliable male sterility by disrupting the tapetum, restorer constructs to restore fertility to male-sterile lines, and pollen disruptor constructs to render construct-containing pollen grains inviable. Two dominant male sterility constructs were found (pMS1:amiAMS and pMS1:mDUO1) which effectively disrupted tapetal function, preventing pollen formation. A restorer construct, pAMS:amimDUO1, was able to consistently restore fertility to male-sterile pMS1:mDUO1 lines by knocking down mDUO1 expression in the tapetum. Additionally, this research suggests a mechanism not tested in this work for restoring fertility to pMS1:amiAMS lines; this would use a miRNA-resistant version of AMS (mAMS) expressed under the AMS promoter to avoid knockdown by amiAMS. pLAT52:amiNPG1 showed potential for use as a pollen disruptor construct, but requires optimisation for consistent results.
Results from the present study in Arabidopsis thaliana will contribute to the development of a DRMS system for use in other flowering plants. The use of a dominant system aims to simplify the process of hybrid breeding, as well as induce complete and reliable male sterility for biocontainment of GM or weedy crops.