Developmental control of heat shock protein expression during pea seed maturation.
AuthorDeRocher, Amy Elizabeth.
Committee ChairVierling, Elizabeth
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractHeat shock proteins (HSPs) are strongly conserved families of proteins induced when an organism is exposed to elevated temperatures. I have studied the expression of two of these protein families, small (s) HSPs and HSP70s in pea (Pisum sativum). Both protein families are induced during seed maturation in addition to being expressed in response to elevated temperatures. Class I cytoplasmic sHSP mRNAs are strongly induced in response to heat stress, comprising over 1% of the mRNA population. HSPs are strongly induced by environmental conditions mimicking conditions plants would experience on hot days. Antiserum raised against a class I sHSP fusion protein detects eight polypeptides in protein from heat stressed leaves. These peptides are induced at leaf temperatures as low as 29°C, and comprise approximately 1% of the SDS soluble protein in 38°C heat stressed leaves, and have a half-life of 38 hours. The low induction temperature and extended half-life of these proteins suggests that they have an important role in the plant life cycle. HSPs are also developmentally regulated during seed maturation, even though the tissue temperature is 10°C below the heat stress induction temperature. Both class I and class II cytoplasmic sHSP mRNAs and proteins accumulate during mid-maturation in cotyledons and during desiccation in axes, and persist in the mature, dry seeds. The amount of protein that accumulates in the maturing seeds is comparable to that induced by a moderate, 34°C, heat stress. Additional sHSPs accumulate if seeds are heat stressed. sHSPs persist for two to three days in germinating seeds. Only five of eight class I sHSP polypeptides accumulate in maturing seeds, and only three of four class II sHSPs are developmentally regulated. HSP70-family proteins are also developmentally regulated during seed maturation. The heat induced mRNA, PsHSP71.2, is coordinately regulated with sHSPs, while a constitutively expressed mRNA, PsHSC71.0, is present throughout seed maturation. The amount of another constitutively synthesized HSP70 mRNA, PsHSP70b, declines in cotyledons as seed maturation progresses. These data suggest that HSPs have a specific role in seed maturation in addition to their role in response to heat stress.
Degree ProgramMolecular and Cellular Biology