Karpov P. Microtubule kinome as an integral regulator of plant tubulin code

The structure of microtubules (MT), as well as sequences of α-, β- and γ-tubulin, is highly conserved. Despite the high conservation, MTs adapt to variety of cellular functions and demonstrate variety of properties. Two different mechanisms can generate MT diversity: the expression of tubulin isotypes, and the generation of different posttranslational modifications (PTMs). It was demonstrated that phosphorylation of mammalian tubulin modulate MTs structure, dynamics and interaction with different associated and transport proteins (MAPs). At the same time, dispite progress in the study of mammalian and yest MT kinoms there are still significant gap in our knowledge of plant MT phosporylation. The objective of the study was to identify plant protein kinases involved in direct phosphorylation of α-/β-/γ-tubulin and kinase-specific phosphorylation sites, to elucidate their function in plant tubulin code. A complete revision of Arabidopsis thaliana kinom (1021 genes) and Homo sapiens protein kinases (105 enzymes) involved in the regulation of the cytoskeleton, cell division, phosphorylation of α-, β-, and γ-tubulin were performed. The closest plants homologes were identified, using bioinformatical and structural biology methods. Bioinformatical evidence was completed by morden cell biology, molecular biology and physiological experiments, modern microscopy, experiments on mutant and transgenic models. It was concluded that in higher plants, phosphorylation of α-, β- and γ-tubulin are associated with 3 AGC kinases (family IRE - IREH1; family S6K - KPK1 and KPK2), 2 CMGC kinases (CDK1 and YAK1), proteinkinase CK2 (subunits: CKA1 / CKA2 / CKB1 / CKB2), CK1 isotype CKL6, 2 isotypes of SnRK1α (KIN10 and KIN11), NIMA-kinase NEK6 (NEK family), and 9 plant Ca2+-dependent protein kinases: 5 CPK family members ( CPK7, CPK14, CPK20, CPK21 and CPK32), 3 CDPK / CRK family members (CRK2, CRK3 and CRK8) and SnAK1-kinase GRIK2. Such comprehensive list of plant tubulin code protein kinases and information on their sites reveals fundamental aspect of plant MTs functional diversity, and display applied interest as the base for new methods and technologies of target influence on plant cytoskeleton.