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The Melonek Group studies the genetic and molecular basis of cytoplasmic male sterility and fertility restoration in plants. Cytoplasmic male sterility (CMS) is a naturally occurring phenomenon caused by mitochondrially-encoded genes that disrupt pollen development, rendering plants sterile. The detrimental effects of CMS genes can be reversed by nuclear-encoded genes that supress the CMS phenotype, restoring pollen production and making plants fertile again. Based on their specific function, these genes are referred to as Restorer-of-fertility or simply Rf. In our lab, we aim to identify the mitochondrial CMS genes on one hand and their nuclear-encoded suppressors, the Rf genes on the other. Once we have both the CMS and Rf genes identified in a given species, we focus on molecular characterisation of their interactions through in vitro protein-RNA binding assays, RNA cleavage tests and in planta transformation.

The majority of Rf genes belong to the pentatricopeptide repeat (PPR) protein family. Recent studies, however, indicate that another group of genes from the family of mitochondrial transcription termination factors (mTERF) are also involved in fertility restoration in plants. To gain a better understanding of the evolution of these two gene families, we perform genome-wide sequence analyses to study their number, genomic organisation, and the presence of unique domains.

In addition to their intriguing biology, the CMS-Rf gene interactions have practical applications in hybrid breeding, where they are used to control self-pollination of plants and enable hybrid crosses. Hybrid cultivars typically show higher and more stable yields in varying weather conditions compared to conventional cultivars, making them highly desirable for plant growers. Research in the Melonek lab, focused on studying the Rf-CMS interactions in crops, contributes to the development of genetic systems for large-scale hybrid seed production in these crops. To achieve this, we collaborate with several public and private institutions in Australia and around the world.