Gibberellins and pea seed development. Expression of the lhi, ls and le 5839 mutations

The gibberellin (GA)-biosynthesis mutations, lhi, ls and Ie5839 have been used to investigate the role(s) of the GAs in seed development of the garden pea (Pisum sativum L.). Seeds homozygous for lhi possess reduced GA levels, are more likely to abort during development, and weigh less at harvest, compared with wild-type seeds due to expression of the lhi mutation in the embryo and/ or endosperm. Compared with wild-type seeds, the lhi mutation reduces endogenous GA1 and gibberellic acid (GA3) levels in the embryo/endosperm a few days after anthesis and fertilizing lhi plants with wild-type pollen dramatically increases GA1 and GA3 levels in the embryo/ endosperm and restores normal seed development. By contrast, the ls and le5839 mutations do not appear to reduce GA levels in the embryo/endosperm of seeds a few days after anthesis, and do not affect embryo or endosperm development. However, both the ls and lhi mutations substantially reduce endogenous GA levels in embryos at contact point (the first day the liquid endosperm disappears). Levels of GAs in seeds from crosses involving the ls and lhi mutations suggest that GAs are synthesised in both the embryo/endosperm and testa and that the expression of ls depends on the tissue and developmental stage examined. These results suggest that GAs (possibly GA1 and/or GA3) play an important role early in pea seed development by regulating the development of the embryo and/or endosperm. By contrast, the high GA levels found in wild-type seeds at contact point (and beyond) do not appear to have a physiological role in seed development. © 1995 Springer-Verlag.