POLLEN AND THE HEAT-SHOCK RESPONSE

The literature related to the expression of heat shock protein (hsp) g enes in developing pollen and in the mature male gametophyte has been surveyed. In general, mature pollen lacks a normal heat shock response . In mature pollen of several species either no hsps are synthesized i n response to heat stress or, if synthesized, only a subset are made a nd the response is weak at both the transcriptional and translational levels, compared to the response in vegetative tissues. In developing pollen, however, a subset of hsps is induced in response to heat shock . In addition, certain hsp genes or heat shock cognate (hsc) genes are activated during normal pollen development in the absence of heat str ess, indicating that these genes are likely to have important developm ental functions. How the distinctive activation pattern of hsp and hsc genes relates to the known sensitivity of pollen to heat stress is di scussed.