The influence of the null le-2 mutation on gibberellin levels in developing pea seeds

摘要

The Le gene of pea encodes a gibberellin 3 beta -hydroxylase. Heterologous expression of the le-2 allele indicated that a truncated protein was produced, confirming that le-2 is a null mutation. The Le expression product was unable to metabolise GA inferior 1 inferior 2, but was able to produce a small quantity of GAs from GA inferior 2 inferior 9. The le-2 mutation had no effect on the levels of GA inferior 1, GA inferior 4 or GA inferior 8 in developing seeds. Measurements of mRNA levels indicate that the Le gene is only weakly expressed in young pea seeds. These results explain why mutant alleles at the Le locus have no major impact on seed development, even though 3 beta -hydroxylated GAs are essential for normal seed development in pea. Rather, a second 3 beta -hydroxylase, with a different substrate specificity, may be expressed in young seeds, resulting in a different biosynthetic pathway leading to the biologically active GAs.