The multiple functions of AVP1 in plant freezing tolerance

Frost-induced crop losses significantly decrease yield. Therefore, identifying genes involved in freezing tolerance is of agricultural importance. Arabidopsis thaliana SFR5 was identified in 1996 as one such gene, due to its mutant’s sensitivity to freezing temperatures. More recently, next generation sequencing has allowed a number of SFR5 candidate genes to be identified, including AVP1. AVP1 is primarily known as a vacuolar proton pumping pyrophosphatase, utilising the energy derived from the hydrolysis of pyrophosphate to transport protons across the tonoplast. In doing so, it impacts the cytoplasmic PPi content. However, the enzyme’s activity has also been shown to influence sucrose phloem loading. One or multiple of these three processes contributes to plant freezing tolerance, among other abiotic stresses. Identifying the function(s) involved in freezing tolerance – through targeted knock out or rescue of individual functions – would facilitate more targeted manipulation of AVP1 in efforts to improve crop freezing tolerance. Thus far, we have confirmed the known freezing sensitive phenotype of sfr5 mutants, and identified similar sensitivity in the known AVP1 mutant fugu5-1. We aim to investigate the proton pumping, PPi hydrolysis and sucrose phloem loading functions in both mutants.