Red light-induced dwarfism and gibberellin 3β-hydroxylase gene expression in Pisum sativum

The growth of the first three internodes of tall (cv. Alaska) and dwarf ( cv. Progress No. 9) cultivars of 6-day-old pea (Pisum sativum L.) seedlings was similar in darkness. Red light inhibited the growth of Progress No. 9 to a greater extent than Alaska, which indicates that the dwarf habit of Progress No. 9 is manifest only in red light. Gene expression of gibberellin (GA) 3beta-hydroxylase, which converts inactive GA(20) to biologically active GA(1), in the internodes of both pea cultivars was higher in darkness than in red light. Changes in the transcript levels of the GA 3beta-hydroxylase gene in dark-grown seedlings of Alaska and Progress No. 9 were monitored after being transferred to red light. The transcript levels in apical buds of both peas increased during the first 3 h and then decreased, which may relate to the morphological changes in the apical buds. Red light gradually decreased the transcript levels in the 3rd internodes of both cultivars and the levels at 24 h were 46% and 44% of the initial levels for Alaska and Progress No. 9, respectively. The differences in transcript levels cannot, therefore, account for the growth habit differences. These results indicate that the growth habit of Progress No. 9 in red light is unlikely to be due to a light-induced blockage in transcription of the GA 3beta-hydroxylase gene.