Characterization of a histidine- and alanine-rich protein showing interaction with calreticulin in rice |
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Authors: | Setsuko Komatsu Asad Jan Yasunori Koga |
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Institution: | (1) National Institute of Crop Science, 2-1-18 Kannondai, Tsukuba 305-8518, Japan;(2) National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan |
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Abstract: | Calreticulin (CRT) is a major calcium-sequestering protein in the endoplasmic reticulum and has been implicated in a variety
of cellular functions. To analyze the function of CRT in rice, a yeast two-hybrid protein interaction assay was used for identifying
interacting proteins. Fourteen of 17 interacting cDNA clones found coded for a novel histidine- and alanine-rich protein (OsHARP)
of 342 amino acid residues. The mRNA expression level of OsHARP was up-regulated in rice seedlings treated with gibberellin
(GA), but not ABA and showed a similar pattern as OsCRT mRNA. Rice plants transformed with the OsHARP promoter-GUS construct
showed GUS staining in the basal parts of leaf sheaths, and although GUS activity increased when treated with GA3, it was not as high an increase as when mRNA was analyzed. To elucidate the role of OsHARP in leaf sheath elongation, antisense
OsHARP transgenic rice lines were constructed. The antisense OsHARP transgenic rice plants were consistently shorter than
the vector control under normal conditions. To examine whether OsHARP expression would affect other proteins, basal leaf sheaths
from antisense OsHARP transgenic rice plants were analyzed using proteomic techniques. In antisense transgenic-rice OsHARP
plants, OsCRT was down-regulated and the levels of 20 other proteins were changed compared to the pattern of the vector control.
These results signify an important role of HARP in rice leaf sheath cell division or elongation and suggest that CRT may interact
with HARP during certain stages of development. |
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