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

The Le gene of pea encodes a gibberellin 3β-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 12, but was able to produce a small quantity of GAs from GA 29. The le-2 mutation had no effect on the levels of GA 1, GA 4 or GA 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 3β-hydroxylated GAs are essential for normal seed development in pea. Rather, a second 3β-hydroxylase, with a different substrate specificity, may be expressed in young seeds, resulting in a different biosynthetic pathway leading to the biologically active GAs.