Abstract Detail

Biochemistry, metabolism, carbon flux

Waduthanthri, Kosala Dinuka [1], Ozga, Jocelyn A. [2], Kaur, Harleen [3], Reinecke, Dennis M. [2].

Gibberellin increases seed sink strength in Pisum sativum L. .

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 a GA deficient mutant lh-2 and a GA-overexpresser line (TG1) with their respective isogenic controls. The lh-2 mutation is a point mutation in an intron of the LH gene (codes for ent-kaurene oxidase that converts ent-kaurene to ent-kaurenoic acid) that reduces the GA₁ levels in young developing pea seeds by 54% (Swain at al., 1993, Planta 191:482). The lh-2 mutation largely affects pea seed growth and development and results in seed abortion (Swain et al, 1997). The GA-overexpresser line 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 our study, we observed marked differences in cell differentiation and expansion in the seed coats and embryos of the lh-2 mutants compared to the wild-type LH line. Seed coats of lh-2 exhibited delayed hypodermal cell differentiation and expansion, and reduced epidermal and ground parenchyma cell expansion compared to the LH line. lh-2 cotyledonary storage parenchyma cell expansion was also reduced compared to the LH line. With respect to photoassimilate partitioning, starch accumulation (8-12 days after anthesis; DAA) in the seed coat and mobilization of seed coat starch to the embryo (16-20 DAA), as well as starch accumulation in the cotyledons, were dramatically reduced of the lh-2 mutant compared to LH. In the GA-overexpresser line TG1, early hypodermal cell differentiation and enhanced hypodermal, epidermal, ground parenchyma and branched parenchyma cell expansion were observed in the seed coat compared to the null control. Starch accumulation in the seed coat 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 null. Greater cell expansion and starch accumulation in the cotyledonary storage parenchyma cells was correlated with an 11 to 34% larger seed size at maturity in TG1 when compared to the null control. 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 embryo.

1 - University of Alberta, 410 Agriculture/Forestry Centre, Edmonton, AB, T6G 2P5, Canada
2 - University of Alberta, Agriculture food and nutritional science, 410 Agriculture/Forestry Centre , Edmonton, Alberta, T6G 2P5 , Canada
3 - University of Alberta, Plant BioSystems Group, Department of Agricultural, Food, and Nutritional Science, Edmonton, AB, T6G 2P5, Canada

Keywords:
Gibberellin
Carbohydrate partitioning
Cell expansion
Seed Development.

Presentation Type: Oral Paper:Papers for Topics
Session: 27
Location: Hall A/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 8:15 AM
Number: 27002
Abstract ID:1229
Candidate for Awards:CSPB President's Award for Best Student Presentation