A reverse-genetics approach to low-oxygen tolerance in Arabidopsis

Anoxia causes an energy crisis in plants because oxygen is required to generate ATP. In anoxia-sensitive species, cell death occurs after sustained anoxia through loss of membrane integrity because insufficient energy is available for proton pumping. Arabidopsis vacuolar H+- pyrophosphatase proton pumps (AVP1) reputedly improve survival in anoxia because pyrophosphate substitutes for ATP to maintain proton pumping. Plants overexpressing AVP1 were grown on medium containing 1% or 0.1% sucrose then in anoxia for up to 2 days. RNA was extracted for qPCR during anoxia or plants were given two weeks in normoxia to recover. Survival and dry weight of roots and shoots after two weeks, and resumption of shoot and root growth, were measured over this period. Survival rates post-anoxia were higher on high-sucrose medium but overexpression of AVP1 in roots increased survival, regardless of sucrose supply. However, biomass was only enhanced by AVP1 overexpression in normoxia. AVP1 expression was strongly induced in roots by anoxia, especially on 0.1% sucrose plates, while exogenous sucrose probably inhibited AVP1 induction. AVP1 is a critical component of acclimation to anaerobiosis as its induction in anoxic roots enhances shoot function during an energy crisis. This is an ideal gene target for improved flood tolerance.