HORMONAL REGULATION OF TUBER PROTEIN SYNTHESIS (PATATIN, GIBBERELLIC ACID, GENE EXPRESSION)
Abstract
Patatin is the major tuber protein of potato (Solanum tuberosum L.). To determine the pattern of its accumulation, patatin distribution was studied in several cultivars under field conditions using rocket immunoelectrophoresis, immunoblotting and Northern blot hybridization. Patatin accounted for 20 to 30% of the soluble protein in mature tubers of all varieties at harvest but was not found in leaves of any of the cultivars except Russet Burbank, which contained trace amounts. Trace amounts were also detected in the stems of two cultivars, Kennebec and Russet Burbank. Roots of all five cultivars contained small amounts of patatin. This root form was immunologically distinct but its polysomal RNA contained patatin mRNA the same size as tuber patatin mRNA. The pattern of patatin's accumulation varied among cultivars and was influenced by environmental conditions. While it has been known that gibberellic acid (GA(,3)) inhibits tuberization, we have shown that exogenous GA(,3) inhibits patatin synthesis in both tubers from whole plants and in cultural systems where the biochemical events of tuberization occur without the morphological ones. This inhibition was substantiated by decreases in the steady-state level of patatin mRNA proportionate to patatin protein decreases. GA(,3)'s dose-dependent effect appears to be specific because even when there was a thirty-fold decrease in patatin mRNA, other mRNAs were readily translatable in rabbit reticulocyte lysate extracts. This GA(,3)-induced inhibition of patatin mRNA accumulation can be explained by a decrease in the transcriptional rate or a differential reduction in patatin mRNA stability.
Degree
Ph.D.
Subject Area
Botany
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