Abstract:

Salinity stress is a major abiotic stress to most plant including rice. It has been reported that gibberellic acid (GA₃) can exert a natural beneficial effect on salt stressed rice. In this paper, the effect of salt stress on rice (Oryza sativa L. cv.Nipponbare) seed germination and the effect of GA₃ on salt-stressed rice were investigated. A proteomic approach was employed to further understand the relieving effect of gibberellin on the inhibition of rice seed germination by salt stress. The 5-day-old rice seedlings were treated with H₂O (control), 5 g L^-1 NaCl (treated group I), and 5 g L^-1 NaCl + 100 μmol L^-1 GA₃ (treated group II) for 48 h respectively. The proteins extracted from buds were separated by two-dimensional gel electrophoresis (2-DE) and analyzed with Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). The results showed that the seed germination of Nipponbare was inhibited by salt stress significantly (see Table 1), while GA₃ could reduce the inhibition significantly (see Table 2). Four protein spots showed differential expression in 2-DE. Three of these proteins were down-regulated (spots 1–3) and one protein disappeared (spots 4) under salt stress. Expression levels of these proteins were recovered partly when treated with GA₃ and NaCl at the same time (see Fig. 1 and Fig. 2). Two protein spots were identified as isoflavone reductase-like protein and phosphoglucomutase (see Table 3). These differential expression proteins may play important role in the mechanism of the relieving effect of gibberellin on the inhibition of rice germination by salt stress.

Key words: Rice, Gibberellin, Salt stress, Proteome