Involvement of Gibberellin in growth and carbohydrate partitioning in developing pea (Pisum sativum L.) seeds

• Author / Creator

  Waduthanthri, Kosala D

• Gibberellins (GAs) are an important class of diterpenoid plant hormones that control various aspects of plant development including seed growth and development. The involvement of GAs during pea (Pisum sativum) seed development was studied by comparing GA deficient mutants; lh-2, lh-1, le-3, ls-1 and a transgenic GA-overexpressor line (TG1) with their respective isogenic or transgenic controls. lh-2 was the most severe GA biosynthesis mutant studied, with marked reduction in seed bioactive GA levels, reduced seed growth, and high seed abortion (Swain et al., 1993, Planta 191:482). Seed coats of lh-2 exhibited delayed hypodermal and reduced epidermal and ground parenchyma cell expansion compared to LH seed coats. lh-2 cotyledonary storage parenchyma cell expansion was also reduced compared to the LH line. With respect to photoassimilate partitioning, starch accumulation (8 to 12 days after anthesis; DAA) in the seed coat and mobilization of seed coat starch to the embryo (14 to 20 DAA), as well as starch accumulation in the cotyledons, were dramatically reduced in the lh-2 mutant compared to LH. The lh-2 mutation delayed the transition of the liquid endosperm from a high to low glucose to sucrose state, and prolonged the complete absorption of the endosperm by the developing embryo by four days compared to that of LH. The other three GA biosynthesis mutants (lh-1, le-3, and ls-1) showed less severe effects on seed growth and development, and seed coat cell expansion. However, starch accumulation in the seed coat was markedly lower in lh-1, le-3, and ls-1 than in their isogenic wild-type (from 8 to 12 DAA), and accumulation of starch in the embryo was delayed (14 to 20 DAA). The GA-overexpressor line TG1 constitutively expresses PsGA3ox1 (LE; a fully functional wild-type GA 3β-hydroxylase gene that encodes 3β-hydroxylase that converts GA20 to GA1) in a semi-dwarf lele pea line (‘Carneval’; le-1; single base-pair mutation in PsGA3ox1) (Reinecke et al., 2013, Plant Physiol 163:929). In the GA-overexpressor line TG1, enhanced hypodermal, epidermal, ground parenchyma and branched parenchyma cell expansion was observed in the seed coat compared to the transgenic control C1. Starch accumulation in the seed coat cells was greater at 10 DAA and mobilization of seed coat starch to the embryo was enhanced from 16 to 20 DAA in TG1 compared to the transgenic control line. The accelerated assimilate partitioning into the seed in TG1 was correlated with larger seed size at maturity. These data support that GAs regulate specific aspects of seed coat and embryo development, and as a result, can modify photoassimilate partitioning into the developing seed.

• Subjects / Keywords

  • Cell expansion
  • Gibberellin
  • Carbohydrate partitioning
  • Pea (Pisum sativum L.) seed growth

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3639KG6C

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.