TISSUE-SPECIFIC LOCALIZATION OF HEAT-STRESS PROTEINS DURING EMBRYO DEVELOPMENT

We report on the stress-independent, tissue-specific expression of the heat-stress protein HSP17 in developing seeds of different plant spec ies and on its intracellular localization. Though HSP17 expression dur ing seed development seems to be a general phenomenon, the isoform pat terns, the relative amounts in embryonic tissues and the intracellular localization show species-specific variations. In contrast to the res ults on the stress-induced protein forming large cytoplasmic aggregate s (heat stress granules) the developmentally expressed HSP17 is mainly found in nuclei. But in addition, a considerable part is also detecte d in protein bodies of mature seeds of Lycopersicon esculentum and Vic ia faba, but not of Zea mays. The mechanism of this transition into th e vacuolar compartment remains to be investigated.