Reference "Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity"

Reference ID

8318

Title

Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity

Source

The Plant journal : for cell and molecular biology, 2003, vol. 36, pp. 189-202

Authors (4)

Liu-W	Xu-Z-H
Luo-D	Xue-H-W

Abstract

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, OsCKI1, was isolated and found to encode a putative 463-aa protein.
RT-PCR and Northern blot analysis indicated that OsCKI1 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 OsCKI1 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 OsCKI1.
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 OsCKI1 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 OsCKI1 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 OsCKI1-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.