Heat‐shock proteins during pollen development in maize

摘要

AbstractIn contrast to sporophytic tissues, mature pollen of higher plants does not synthesize the typical set of heat‐shock proteins (HSPs) in response to a marked temperature upshift. Immature grains, however, seem able to do so, at least partially. We investigated the characteristics of HSP synthesis throughout the male gametophytic phase in maize and compared gametophytic and sporophytic heat‐shock responses. One‐dimensional Sodium dodecyl sulfate‐polyacryl‐amide gel electrophoresis technique (SDS‐PAGE) of newly synthesized proteins revealed that immature pollen synthesizes HSPs, some of which are not induced in sporophytic tissues. The heat‐shock response appeared to be related to microgametophytic developmental stages. The strongest response was found in uninucleate microspores: at this stage, in addition to the sporophytic 102, 84, 72, and 18 kD HSPs, three other polypeptides of 74, 56, and 46 kD were observed. In the binucleate and trinucleate stages, only a reduced synthesis of few HSPs could be induced, and differences between genotypes were observed. In germinating pollen, HSP synthesis was not induced under a voriety of heat‐stress conditions; however, the consti‐tutive synthesis of two polypeptides of the same molecular weight, 72 and 64 kD, as two HSPs was observed. The biological significance of these res