A comparison of desiccation-related proteins (dehydrin and QP47) in peas (Pisum sativum)

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Abstract
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 degradation have been examined during germination. Tissue locations were determined by immunocytochemistry using polyclonal antibodies raised against a conserved dehydrin amino acid sequence and against purified QP47. In embryonic axis and cotyledon cells, QP47 and dehydrin were distributed uniformly with no apparent nuclear or organellar specificity. Both proteins were present in 24 h-imbibed axes that had not initiated radicle growth but were completely absent from 24 h-imbibed axes that had begun to grow. The amounts of QP47 and dehydrin in embryonic axes decreased with time after the start of imbibition and were undetectable by 48 h. When germination was prevented by polyethylene glycol (PEG) or abscisic acid (ABA), both proteins remained at their original amounts. Thus, both QP47 and dehydrin disappeared coincidently with the beginning of growth and not simply as a function of the time after imbibition. QP47 persisted in cotyledons until at least 31 days into seedling growth, whereas dehydrin was not detectable in cotyledons after 7 days. Dehydrin, but not QP47, could be re-induced in pea shoots and cotyledons by dehydration. The timing of degradation of both proteins was correlated with the loss of desiccation tolerance during germination of pea axes.