Discovering early light-induced phosphoproteins that respond to photoreceptor activation

Abstract

Phosphorylation state of a protein is a key aspect that potentially governsitsstability, activation, localization, activity and functionality. Several signaling pathways involvechangesin phosphorylation as meansof transducing effectively different stimuli. Among them, light triggers complex signaling networks that result in physiological and developmental responses. Phosphorylation–dephosphorylation events provide a powerful mechanism that links light perception to final response. Westudied theearly light-induced phosphoproteomein Arabidopsisthalianathrough Label freeLCMS/MS proteomic approach. 41 phosphopeptides out of the 2267 identified,changed significantly their phosphorylation statein responsetolight. One phosphopeptide increased while 3 decreased their phosphor-isoforms in the presence of photoactivated photoreceptors. Currently, we are studying the phosphorylation dynamics, biological functions and cellular localization of two of these phosphoproteins which are potentially involved in early photomorphogenesis events. Oneis a transcription factor that interacts with COP1. The other is a negative regulator of SKD1 involved in endosomal trafficking of multivesicular bodies. Arabidopsis knock-out plants for its gene exhibit photomorphogenicresponse under red light. Here, weidentified two early light induced phosphoproteins that reveal photoreceptors dependent phosphoregulation.