Effects of plasmotype variations on circadian clock rhythm during temperature shift in barley

Circadian clock facilitates the coordination of the internal rhythms of an organism to daily environmental conditions for maintaining growth and development. We recently revealed that the more peripheral rhythmicity of barley plants shows plasticity, i.e. change in the circadian period and amplitude of photosynthetic activities including non-photochemical quenching (NPQ), under changing temperatures. Using the SensyPAM platform, we identified significantly differential clock robustness between doubled haploids that carry different plasmotypes (chloroplast and mitochondria). The carriers of the Northern Hermon vs Southern Ashkelon plasmotype are more robust during temperature shift compared for the clock period. Sequence comparison between the chloroplast genome of Ashkelon and Hermon identified several candidates with non-synonymous mutation including two SNP in gene encoding the RNA polymerase C1 (rpoC1). We, therefore, analysed the Arabidopsis chloroplastic rpoC1 mutants for clock phenotype and noticed decelerated period compared to wild type during optimal temperature (22⁰C). Furthermore, we complemented Arabidopsis rpoC1 mutants and tobacco with the wild barley alleles to test for possible causality of the non-synonymous chloroplast mutations, and experience complementation of phenotype. In addition, we scaled down chloroplast DNA extraction methods to allow isolation of chloroplast DNA from 96 B1K lines with nucleotype SNP information to allow GWAS analysis that will expand our view of possible cytonuclear interaction and their consequences on robustness. Integrating genetic, physiological and molecular information across barley, tobacco and Arabidopsis will allow identification and functional analysis of chloroplast gene diversity and its possible role in maintaining phenotypic robustness.