Effect of Heat Shock on the Synthesis of Small Cytoplasmic
RNAs in Higher Plants

N. S. Polimbetova, S. Sh. Zhanybekova, A. V. Li, and B. K. Iskakov

Aitkhozhin Institute of Molecular Biology and Biochemistry, Almaty, Kazakhstan

Received January 10, 1996

Abstract—The effect of heat shock on changes in the pattern of small cytoplasmic RNAs (scRNAs) was stud-
ied in cells of germinating wheat, rye, and pea embryos as well as in wheat embryo calluses and tobacco leaf
protoplasts. A novel scRNA of about 135 nucleotides (5.3S RNA), discovered for the first time in wheat
embryos, was shown to be a common cellular component in all plant tissues under study; however, it was not
detected in rabbit reticulocytes. The amount of 5.3S RNA increased five–six times under heat-shock conditions,
it was located mainly in ribosomal fraction and was not detected as a free form in cytosol. Heat shock induced
5.3S RNA synthesis only in vivo. Heating of nucleus-free extract in vitro under the same conditions did not
result in any increase in 5.3S RNA content. A direct correlation was found between 5.3S RNA accumulation
and the level of heat-shock protein (HSP) synthesis in wheat embryos. The data obtained suggest that 5.3S RNA
may be involved in the regulation of HSP synthesis in plant cells.

Key words: Triticum aestivum - embryos - heat shock - small RNAs - ribosomes - heat-shock protein synthesis

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