Abstract

GA 20-oxidase is a key enzyme involved in gibberellin (GA) biosynthesis. To investigate the roles of OsGA20ox2 in regulating plant growth and development, we used reverse genomic approach to generate dwarf transgenic rice plants with antisense technology. OsGA20ox2 nucleic acid sequence includes three exons and two introns. We constructed three antisense vectors named pA1CK, pA2CK, pACK, respectively, major containing the first exon, the second exon, and the whole cDNA sequence of OsGA20ox2 gene. Through Agrobacterium-mediated transformation of rice, six dwarf lines were obtained from antisense vector pACK. Three dwarf lines (5101 to 5103) in T₁ generation displayed severe dwarf in height (12.31 cm, 11.4% of wild type plants), fewer tiller numbers (4.87, 35.3% of wild type plants), smaller dark green leaves, shorter internode length (7.05 cm, 10.9% of wild type plants), and seed abortion compared to the wild type plants. Other three dwarf lines in T₂ generation (5104 to 5106) showed dwarf (56.18 to 60.64 cm, 52.0 to 56.1% of wild type plants), late flowering, few tiller numbers (11.60 to 12.60, 84.1 to 91.3% of wild type plants), short internode length (34.69 to 35.37 cm, 53.4 to 54.5% of wild type plants), 100-seed weight reduction (1.53 to 1.57 g, 74.9 to 75.8% of wild type plants), and reduced seeds reproductive. The results indicate that dwarf lines decreased expression ofOsGA20ox2 gene in stem and panicle but no change in root. These results show that the antisense OsGA20ox2 gene restricted rice architecture, suggesting thatOsGA20ox2 was required for panicles and stem development. We further showed that the antisense dwarf lines could be restored to normal plant height by applying exogenous GA₃. Results also demonstrate that antisense expression of OsGA20ox2affected plant stature and development.

Key words: OsGA20ox2, antisense, dwarf, development.

Abbreviation

Abbreviations: PCR, Polymerase chain reaction; CTAB, cetyl trimethyl ammonium bromide; GA, gibberellin.