.However,to our knowledge this is the first report of a transgenic crop incorporating a single RCA gene to test growth and developmental heat tolerance. Our hypothesis was that small instantaneous improvements in photosynthetic carbon gain in the transgenic plants exposed to heat will cumulatively result in major impacts on yield. Specifically, we propose that plants that fix CO2 more efficiently during successive weeks of vegetative growth during high temperature can subsequently re-mobilise these carbohydrates into grain. The impact of a variant form of RCA throughout the lifecycle is not predictable a priori and thus long-term observations of these aspects of plant performance in transgenic plants are essential. In this study, the efficiency with which the RCA transgene was expressed was estimated using multiple reaction monitoring high-resolution proteomics (MRM-HR), thus enabling correlations between the phenotypic responses and the level of O.australiensis recombinant Rca abundance and total Rca protein abundance.