Expression of the Heat Shock Response in a Tomato Interspecific Hybrid Is Not Intermediate between the Two Parental Responses

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Abstract
While it is apparent that the heat shock response is ubiquitous, variabilities in the nature of the heat shock response between closely related species have not been well characterized. The heat shock response of three genotypes of tomato, Lycopersicon esculentum, Lycopersicon pennellii, and the interspecific sexual hybrid was characterized. The two parental genotypes differed in the nature of the heat shock proteins synthesized; the species-specific heat shock proteins were identified following in vivo labeling of leaf tissue with [35S]methionine and cysteine. The duration of, and recovery from, heat shock varied between the two species: L. esculentum tissue recovered more rapidly and protein synthesis persisted longer during a heat shock than in the wild species, L. pennellii. Both species induced heat shock protein synthesis at 35.degree.C and synthesis was maximal at 37.degree.C. The response of the F1 to heat shock was intermediate to the parental responses for duration of, and recovery from, heat shock. In other aspects, the response of the F1 to heat shock was not intermediate to the parental responses: the F1 induced only half of the L. esculentum specific heat shock proteins, and all of the L. pennellii specific heat shock proteins. A discussion of the inheritance of the regulation of the heat shock response is presented.