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Roles of OsCKI 1, a rice casein kinase I, in root development and plant hormone sensitivity
Author(s) -
Liu Wei,
Xu ZhiHong,
Luo Da,
Xue HongWei
Publication year - 2003
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2003.01866.x
Subject(s) - biology , brassinosteroid , complementary dna , abscisic acid , transgene , auxin , kinase , casein kinase 1 , gene expression , casein kinase 2 , lateral root , microbiology and biotechnology , genetically modified crops , biochemistry , arabidopsis , gene , protein kinase a , cyclin dependent kinase 2 , mutant
Summary Casein kinases are critical in cell division and differentiation across species. A rice cDNA fragment encoding a putative casein kinase I (CKI) was identified via cDNA macroarray under brassinosteroid (BR) treatment, and a 1939‐bp full‐length cDNA, OsCKI 1, was isolated and found to encode a putative 463‐aa protein. RT‐PCR and Northern blot analysis indicated that OsCKI 1 was constitutively expressed in various rice tissues and upregulated by treatments with BR and abscisic acid (ABA). Enzymatic assay of recombinant OsCKI1 proteins expressed in Escherichia coli showed that the protein was capable of phosphorylating casein. The physiological roles of OsCKI 1 were studied through antisense transgenic approaches, and homozygous transgenic plants showed abnormal root development, including fewer lateral and adventitious roots, and shortened primary roots as a result of reduced cell elongation. Treatment of wild‐type plants with CKI‐7, a specific inhibitor of CKI, also confirmed these functions of OsCKI 1. Interestingly, in transgenic and CKI‐7‐treated plants, exogenously supplied IAA could restore normal root development, and measurement of free IAA content in CKI‐deficient primary and adventitious roots revealed altered auxin content, indicating that OsCKI 1 is involved in auxin metabolism or that it may affect auxin levels. Transgenic plants were less sensitive than control plants to ABA or BR treatment during germination, suggesting that OsCKI 1 may be involved in various hormone‐signaling pathways. OsCKI1‐GFP fusion studies revealed the localization of OsCKI1 to the nucleus, suggesting a possible involvement in regulation of gene expression. In OsCKI 1‐deficient plants, differential gene expression was investigated using cDNA chip technology, and results indicated that genes related to signal transduction and hormone metabolism were indeed with altered expression.