A COMPARISON OF DESICCATION-RELATED PROTEINS (DEHYDRIN AND QP47) IN PEAS (PISUM-SATIVUM)

Dehydrin and QP47, proteins present in mature pea seeds (Pisum sativum ), have been proposed to play protective roles during desiccation. To identify possible relationships between these proteins and desiccation tolerance, their tissue locations and patterns of synthesis and degra dation have been examined during germination. Tissue locations were de termined by immunocytochemistry using polyclonal antibodies raised aga inst a conserved dehydrin amino acid sequence and against purified QP4 7. In embryonic axis and cotyledon cells, QP47 and dehydrin were distr ibuted uniformly with no apparent nuclear or organellar specificity. B oth proteins were present in 24h-imbibed axes that had not initiated r adicle growth but were completely absent from 24h-imbibed axes that ha d begun to grow. The amounts of QP47 and dehydrin in embryonic axes de creased with time after the start of imbibition and were undetectable by 48 h. When germination was prevented by polyethylene glycol (PEG) o r abscisic acid (ABA), both proteins remained at their original amount s. Thus, both QP47 and dehydrin disappeared coincidently with the begi nning of growth and not simply as a function of the time after imbibit ion. QP47 persisted in cotyledons until at least 31 days into seedling growth, whereas dehydrin was not detectable in cotyledons after 7 day s. Dehydrin, but not QP47, could be re-induced in pea shoots and cotyl edons by dehydration. The timing of degradation of both proteins was c orrelated with the loss of desiccation tolerance during germination of pea axes.