Usefulness and Molecular Mechanism of Seed-Specificity Introduced by AtBZR1 and AtBES1 to Improve Seed Yield and Quality in Arabidopsis thaliana

다국어 초록 (Multilingual Abstract)

This study generated the transgenic Arabidopsis lines pAt5g54000-AtBZR1::Col-0 and pAt5g54000-AtBES1::Col-0, in which Arabidopsis BZR1 and BES1 (AtBZR1 and AtBES1) were seed-specifically expressed with pAt5g54000, a seed-specific promoter. Semi-quantitative RT-PCR and GUS-staining analysis demonstrated that the inserted AtBZR1 and AtBES1 were concentrated in seeds in siliques of transgenic plants. Seed number, length, width, and mass increased in the pAt5g54000-AtBZR1::Col-0 and pAt5g54000-AtBES1::Col-0 mutants compared to untransformed Arabidopsis. The endogenous levels of primary metabolites, such as carbohydrates, proteins, and lipids, in transgenic seeds were also higher than those in wild-type seeds, indicating that both seed size and quality are improved by seed-specific expression of AtBZR1 and AtBES1 in Arabidopsis. In both transgenic Arabidopsis seeds, relative to wild-type seeds, the expression of positive regulatory genes involved in determining seed size, such as SHORT HYPOCOTYL UNDER BLUE1 (AtSHB1), MINISEED3 (AtMINI3), and HAIKU2 (AtIKU2), was increased by up-regulation of AtBZR1 and AtBES1 as well as down-regulation of ABA Deficient 2 (AtABA2) and ABA Insensitive 5 (AtABI5). This result suggests that AtBZR1- and AtBES1-mediated signaling pathways such as AtBZR1/AtBES1 → AtSHB1 → AtMINI3 → AtIKU2 and AtBZR1/AtBES1 → AtABA2, and/or AtABI5 → AtSHB1 → AtMINI3 → AtIKU2 increase the yield and quality of seeds in transgenic Arabidopsis. Taken together, our findings demonstrated the usefulness and applicability of seed-specific introduction of AtBZR1 and AtBES1 encoding key transcription factors in brassinosteroid signaling to improve seed yield and quality in Arabidopsis.