title: Plastid casein kinase 2 knockout reduces abscisic acid (ABA) sensitivity, thermotolerance, and expression of ABA- and heat-stress-responsive nuclear genes.
abstract: Plastid casein kinase 2 (CK2) is a major Ser/Thr-specific enzyme for protein phosphorylation in the chloroplast stroma and its kinase activity is regulated by redox signals. To understand the role of CK2 phosphorylation of chloroplast proteins in abiotic stress signalling, an Arabidopsis plastid CK2 (CKA4) knockout mutant was investigated in terms of the plant response to abscisic acid (ABA) and heat stress. CKA4 expression was upregulated by ABA and heat treatment. The cka4 mutant showed reduced sensitivity to ABA during seed germination and seedling growth, and increased stomatal aperture and leaf water loss with a slightly reduced leaf ABA level. The cka4 mutant was more sensitive to heat stress than the wild-type Columbia-0. The expression levels of a number of genes in the ABA regulatory network were reduced in the cka4 mutant. Many heat-upregulated genes (heat-shock factors and heat-shock proteins) were also reduced in the cka4 mutant. The cka4 mutant showed reduced expression levels of plastid-encoded RNA polymerase target genes (atpB and psbA). CKA4 knockout mutation also resulted in a reduction in expression of some critical genes (PTM, ABI4, and PRS1) involved in retrograde signalling from the chloroplast to the nucleus. Similar results were observed in mutant plants with the knockout mutation in both CKA4 and CKA3, which encodes a nuclear CK2 α3 subunit. CKA3 expression was not responsive to ABA and heat stress. These results suggest that CKA4 is an enhancing factor in abiotic stress signalling through modulating the expression of some molecular players in retrograde signalling.
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Hongping
authors.initials: H
authors.lastname: Chang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Xiutao
authors.initials: X
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Congying
authors.initials: C
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Xiao
authors.affiliation: Hunan Provincial Key Laboratory of Phytohormones and Growth Development, Hunan Agricultural University, Changsha, 410128, PR China.
authors.forename: Langtao
authors.initials: L
authors.lastname: Xiao
authors.affiliation: CSIRO Plant Industry, 306 Carmody Road, St Lucia, QLD 4067, Australia Gang-Ping.Xue@csiro.au gxh@hnu.edu.cn.
authors.forename: Gang-Ping
authors.initials: GP
authors.lastname: Xue
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha 410082, PR China Gang-Ping.Xue@csiro.au gxh@hnu.edu.cn.
authors.forename: Xinhong
authors.initials: X
authors.lastname: Guo
mesh_terms: D000040:Abscisic Acid / Q000502:physiology*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D047390:Casein Kinase II / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D006358:Hot Temperature; D008315:Malondialdehyde / Q000378:metabolism; D054046:Plant Stomata / Q000502:physiology; D011392:Proline / Q000378:metabolism; D013312:Stress, Physiological; D014867:Water / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D014867:Water; D008315:Malondialdehyde; D000040:Abscisic Acid; D011392:Proline; D047390:Casein Kinase II
keywords: ABA insensitivity; gene expression; knockout mutation; plastid casein kinase 2; retrograde signalling; thermotolerance.