Gene expression in Brassica tissues and species following heat shock

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Abstract
Several tissues from the three oilseed Brassica species have been analyzed for polypeptides synthesized in vivo and in vitro under control (23 °C) and heat-shock conditions. The various tissues have characteristically unique patterns of polypeptide synthesis, the general pattern being maintained following heat shock. In addition, all tissues exhibit synthesis of a set of qualitatively similar heat shock protein (HSP) that differ, however, in relative intensity among tissues. Synthesis of control polypeptides as well as high molecular-weight HSP is similar in hypocotyls of the three genomically interrelated species B. napus, B. campestris, and B. juncea; however, the three species exhibit variation in in vivo and in vitro synthesized polypeptides in the 18 000–27 000 molecular-weight region, with several prominent differences in the number and distribution of the major class of low molecular-weight (20 000) HSP. Several of the HSP appear to be unique to B. juncea and one is unique to B. napus. Immunochemical studies of in vitro synthesized Brassica polypeptides using antisera to maize HSP of molecular weight 18 000 substantiate the observed differences in synthesis of various members of the 20 000 molecular-weight HSP family among the three species, and indicate that the Brassica low molecular-weight HSP are immunologically similar to the small HSPs of other plants including maize, soybean, pea, and Arabidopsis.