Arabidopsis serine/threonine/tyrosine protein kinase phosphorylates oil body proteins that regulate oil content in the seeds

Abstract

Protein phosphorylation is an important post-translational modification that can regulate the protein function. The current knowledge on the phosphorylation status of plant oil body (OB) proteins is inadequate. This present study identifies the distinct physiological substrates of Arabidopsis serine/threonine/tyrosine protein kinase (STYK) and its role in seed oil accumulation; the role of Arabidopsis OLE1, a major seed OB protein has also been elucidated. In vitro kinase assay followed by mass spectrometry identifies residue that are phosphorylated by STYK. Further, co-expression of OLE1 and STYK in yeast cells increases the cellular lipid levels and reduces the total lipid when OLE1 was replaced with OLE1T166A. Moreover, in vivo experiments with OB isolated from wild-type and styk knock-out lines show the ability of STYK to phosphorylate distinct OB proteins. OLE1T166A mutant and Arabidopsis styk mutant demonstrate the significant reduction of its substrate phosphorylation. styk mutant line significantly reduces the amount of total seed oil as compared to wild-type seeds. Together, our results provide the evidences that Arabidopsis At2G24360 (STYK) is phosphorylating oil body proteins and the phosphorylation regulates the oil content in Arabidopsis seeds.

Genome-wide identification and analysis of Oleosin gene family in four cotton species and its involvement in oil accumulation and germination

“…The replacement of Pro residue can lead to abnormal targeting of the OB [ 19 ]. The N- and C-terminal amphiphilic domains, located on the surface of the oil body, can not only maintain the size of the OB through their steric hindrance and electronegative repulsion [ 20 ] but also regulate the OB by combining it with metabolic enzymes and regulatory proteins [ 21 – 23 ]. Take together, oleosins are involved in the oil bodies regulation and biosynthesis, and metabolism of lipid [ 24 , 25 ].…”

A Cytosolic Protein Kinase STY46 in Arabidopsis thaliana Is Involved in Plant Growth and Abiotic Stress Response

“…Members of the STY kinase family are dual-specificity kinases that possess catalytic Ser/Thr and Tyr domains, and they regulate some plant metabolic and developmental processes through phosphorylation of target proteins [24,25]. For example, STY protein kinases appear to have important roles in ammonium transport in rice seedling roots [26], in storage oil accumulation in Arabidopsis siliques [27], and in stress response and seed development in cucumber and peanuts [28][29][30].…”

Interspecific Variation in the Unsaturation Level of Seed Oils Were Associated With the Expression Pattern Shifts of Duplicated Desaturase Genes and the Potential Role of Other Regulatory Genes

“…Some genes involved in protein post-translational modification, such as protein phosphorylation (Protein kinase superfamily protein) and ubiquitination ( UBC5 ), were also tightly co-expressed with fatty acid biosynthesis genes. Previous studies have shown that a serine/threonine/tyrosine protein kinase participated in the regulation of the content and composition of the Arabidopsis seed oil by mediating phosphorylation of oil body proteins ( Ramachandiran et al, 2018 ). It has also been revealed that the seed-expressed casein kinase I enhanced the bHLH -mediated transactivation of the FAD2 gene promoter via phosphorylation of the bHLH transcription factor ( Kim et al, 2010 ), while the ubiquitin proteasome pathway modulated FAD3 protein amounts in response to temperature ( O’Quin et al, 2010 ).…”