Differential expression of gibberellin 20 oxidase gene induced by abiotic stresses in Zoysiagrass (Zoysia japonica)

The gibberellin 20-oxidase gene (GA20) plays an important role in plant growth and development. Differential expression of Zoysiagrass (Zoysia japonica Steud.) gibberellin 20 oxidase gene (ZjGA20) induced by abiotic stresses has not been reported. In this investigation, we first reported the differential expression of ZjGA20 in different Z. japonica tissues including root, young leaf, senescent leaf, blade, sheath, and stolon, as well as differential expression induced by abiotic stresses including low temperature (4A degrees C), H2O2(8 mu M), salt stress (250 mM NaCl), 25% PEG(6000), and high temperature (42A degrees C) by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Higher expression of ZjGA20 was observed in young leaf and sheath, compared to root, senescent leaf, blade, and stolon. Among different abiotic stresses, expression of ZjGA20 decreased under low temperature, 25% PEG(6000), and high temperature. The highest expression of ZjGA20 was obtained when plants were treated with 8 mu M H2O2 for 10 h and with 250 mM NaCl for 5 h. The analysis of the MDA content, POD activity, and permeability of the plasma membrane demonstrated that application of exogenous GA(3) recovered tissue damage derived from low temperature treatment. In addition, the expression of ZjGA20 increased under low temperature stress. These results demonstrated that expression of ZjGA20 was regulated by abiotic stresses and the damage derived from abiotic stresses could be rescued by exogenously applied plant growth regulator GA(3). Further more, exogenous gibberellin and salicylic acid (SA) alleviated the growth inhibition and death of the seedlings under stresses. The SA content in the seedlings treated with 80 mu M GA(3) was far greater than the control (with H2O) and plants under stress treatments. These data suggest that exogenous addition of GA(3) is able to counteract the inhibitory effects of these adverse environmental conditions in Zoysiagrass growth through modulation of SA biosynthesis. This is the first study of differential expression of gibberellin 20 oxidase gene and growth regulation of GA(3) in Zoysiagrass under stresses.