Abstract
Plant growth depends on the diurnal regulation of cellular processes,
but it is not well understood if and how transcriptional regulation
controls diurnal fluctuations at the protein-level. Here we report a
high-resolution Arabidopsis thaliana (Arabidopsis) leaf rosette proteome
acquired over a 12 h light : 12 h dark diurnal cycle and the
phosphoproteome immediately before and after the light-to-dark and
dark-to-light transitions. We quantified nearly 5000 proteins and 800
phosphoproteins, of which 288 fluctuated in their abundance and 226
fluctuated in their phosphorylation status. Of the phosphoproteins, 60%
were quantified for changes in protein abundance. This revealed six
proteins involved in nitrogen and hormone metabolism that had concurrent
changes in both protein abundance and phosphorylation status. The
diurnal proteome and phosphoproteome changes involve proteins in key
cellular processes, including protein translation, light perception,
photosynthesis, metabolism and transport. The phosphoproteome at the
light-dark transitions revealed the dynamics at phosphorylation sites in
either anticipation of or response to a change in light regime.
Phosphorylation site motif analyses implicate casein kinase II and
calcium/calmodulin dependent kinases among the primary light-dark
transition kinases. The comparative analysis of the diurnal proteome and
diurnal and circadian transcriptome established how mRNA and protein
accumulation intersect in leaves during the diurnal cycle of the plant.