Thermal Shift-induced Gene Expression And Regulation In Maize (zea Mays L)

Rapid elevation in the incubation temperature of maize seedlings leads to the new and(or) enhanced synthesis of a group of heat shock polypeptides (HSPs). The response is: (a) rapid (HSP synthesis is detectable within 15 minutes following thermal shifts); (b) reversible (the pre-shift pattern of polypeptide synthesis is re-established when seedlings are returned to the control temperature); and (c) transitory (maintenance of seedlings at the elevated temperature leads to a gradual reduction of HSP production and the establishment of a new pattern of polypeptide synthesis). The synthesis of an apparently identical set of HSPs is noted in maize plumules, mesocotyls, radicles and young leaves.;In vitro translational analyses indicate that the HSPs represent the products from translation of polyadenylated messenger RNAs. Post-transcriptional and post-translational regulatory mechanisms may determine the final array of polypeptides which are produced.;In maize, changes in the synthesis of polypeptides and their mRNAs appear to represent a normal response not only to heat shock but to any thermal shift; the array of gene products and the degree to which they are synthesized are determined by several factors including: (a) the initial growing temperature; (b) the temperature shift increment; (c) the temperature regime within which the shift is carried out; (d) the rate of increase of seedling temperature; and (e) the duration of the temperature treatment.;While HSP synthesis in maize is analogous to the response observed in other species, maize HSPs exhibit different degrees of immunological relatedness to HSPs from other organisms. High molecular weight HSPs from maize, soybean and pea exhibit similar degress of cross-reactivity with antibodies to maize 73-89 kD HSPs. Antibodies to maize 18 kD HSPs react strongly with maize 18 kD HSPs, to a lesser extent with soybean 18 kD HSPs, and very little with 17 kD HSPs from pea. Quail, mouse and tadpole HSPs do not react with antibodies to maize HSPs. Thus, while the synthesis of polypeptides in response to thermal shifts or stresses may be universal, differences exist in the classes of polypeptides which are synthesized, and in the degree of relatedness of polypeptides of apparently similar size from different species