Os07g0694700

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Annotated Information

Function

Little is known about the individual functions of the APX isozymes in rice, partly because of the difficulty in obtaining sufficient amounts of homogeneous and active isozymes for analysis. The authors introduced cDNA clones (APXa and APXb) encoding rice APX isozymes into the expression vector pGEX-6p-3 to allow expression as a glutathione- S-transferase (GST) fusion protein in Escherichia coli, and obtained homogeneous, active recombinant proteins with high yields by using an optimized procedure[1].

Expression

RNA gel blot analysis showed that the transcription of the OsAPx2 gene increased significantly with time of exposure to NaCl, NaHCO3, and PEG 6000[2]. APX isozymes occur in several cell compartments and occur in many plants, including Arabidopsis, spinach, pumpkin, tobacco, soybean, potato and rice. Plant APX isoforms act differently in response to stress and in different developmental stages[1]. rice plants that overexpress OsAPXa and have increased APX activity. The effect of increased APX activity on the levels of H(2)O(2) and lipid peroxidation were determined by measuring H(2)O(2) levels and malondialdehyde (MDA) contents in spikelets during cold treatments at the booting stage. The levels of H(2)O(2) and the MDA content increased by 1.5-fold and twofold, respectively in WT plants subjected to a 12 °C treatment for 6 days. In contrast, transgenic lines showed small changes in H(2)O(2) levels and MDA content under cold stress, and H(2)O(2) levels and MDA content were significantly lower than in WT plants. APX activity showed negative correlations with levels of H(2)O(2) and MDA content, which increased during cold treatment. Cold tolerance at the booting stage in transgenic lines and WT plants was evaluated. Spikelet fertility was significantly higher in transgenic lines than in WT plants after a 12 °C treatment for 6 days. These results indicate that higher APX activity enhances H(2)O(2)-scavenging capacity and protects spikelets from lipid peroxidation, thereby increasing spikelet fertility under cold stress[3].

Evolution

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Labs working on this gene

Stress Molecular Biology Laboratory, Northeast Forestry University, Harbin, 150040, P.R. China

Asian Natural Environment Science Center (ANESC), The University of Tokyo, Nishitokyo City, Tokyo, Japan

Research Laboratory for Agricultural Biotechnology and Biochemistry (RLABB), GPO Box 8207, Kathmandu, Nepal

National Institute of Advanced Industrial Science and Technology (AIST), Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

Department of Agronomy, National Taiwan University, Taipei, Taiwan, ROC

References

1. Guan Q, Takano T, Liu S. Genetic Transformation and Analysis of Rice OsAPx2 Gene in Medicago sativa[J]. PloS one, 2012, 7(7): e41233.

2. Lu Z, Takano T, Liu S. Purification and characterization of two ascorbate peroxidases of rice (Oryza sativa L.) expressed in Escherichia coli[J]. Biotechnology letters, 2005, 27(1): 63-67.

3. Sato Y, Masuta Y, Saito K, et al. Enhanced chilling tolerance at the booting stage in rice by transgenic overexpression of the ascorbate peroxidase gene, OsAPXa[J]. Plant cell reports, 2011, 30(3): 399-406.

4. Teixeira F K, Menezes-Benavente L, Galvão V C, et al. Rice ascorbate peroxidase gene family encodes functionally diverse isoforms localized in different subcellular compartments[J]. Planta, 2006, 224(2): 300-314.

5. Tsai Y C, Hong C Y, Liu L F, et al. Expression of ascorbate peroxidase and glutathione reductase in roots of rice seedlings in response to NaCl and H(2)O(2). Journal of plant physiology, 2005, 162(3): 291-299.