Close relationship between the state of the oxygen evolving complex and rice cold stress tolerance

Abstract

The results of the present work suggested arelationship between the growth stability and functional/structural parametersassociated to the primary photochemistry and oxygen evolving complex (OEC) intolerant rice plants under suboptimal low temperatures (SLT) stress. This wasconcluded from the absence of changes in net photo synthetic rate and infraction of reaction centers to reduce quinone A, and very small changes inP680 efficiency to trap and donate electrons to quinone A and in fraction ofactive OEC in tolerant plants under cold stress but not in sensitive plants.The SLT stress also induced OEC activity limitations in both genotypes, but ina greater extent in sensitive plants. However, an assay using an artificialelectron donor to replace OEC indicated that the P680+ capacity toaccept electrons was not altered in both genotypes under SLT stress from thebeginning of the stress treatment, suggesting that the OEC structure stabilityis related to rice SLT tolerance to sustain the photosynthesis. This hypothesiswas also supported by the fact that tolerant plants but not sensitive plantsdid not alter the gene expression and protein content of PsbP under SLT stress,an OEC subunit with a role in stabilizing of OEC structure.