Os06g0561000

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OsMIOX, a myo-inositol oxygenase gene, improves drought tolerance through scavenging of reactive oxygen species in rice[1].

Annotated Information

Function

OsMIOX has a specific function in drought stress tolerance by decreasing oxidative damage. The expression levels of ROS scavenging genes, CatB, POD1, POD2, APX1 and APX2 were indeed up-regulated, which may contribute to decrease the accumulation of ROS in OsMIOX-overexpressing plants under drought stress[1].

Mutation

Transgenic lines and wild type[1]:

  • The transgenic rice lines overexpressing OsMIOX showed obviously improved growth performance in the medium containing 200 mM mannitol.
  • Further, the survival rate of leaves from the transgenic rice lines was significantly higher than that of the wild type plants under polyethylene glycol treatment.
  • It was discovered that the activity of ROS scavenging enzymes and proline content, as well as the transcript levels of many ROS scavenging genes were significantly increased in transgenic plants compared to the wild type plants under drought stress conditions.
  • Four-week-old transgenic homozygous lines and the WT were treated with 20% PEG6000 for 6 days and then allowed to recover for 17 days.
    • The transgenic lines recovered more quickly than the WT, and showed a total recovery of 38–46%, while the WT plants were severely affected by drought stress and had only 18–22% recovery.
    • The water loss was determined by comparing the rates of change in fresh weight of the detached leaves. The water loss assay showed that the transgenic lines had a slower dehydration rate compared to WT, with a 0.28–2.6% lag from the beginning to 6 h after dehydration.

Expression

  • OsMIOX was expressed predominantly in the roots and induced by drought, H2O2, salt, cold and abscisic acid. OsMIOX was more strongly induced in IRAT109 than that in Nipponbare under all treatments except for cold. The expression peak of OsMIOX was later in IRAT109 than that in Nipponbare under all treatments except salt and cold, indicating that the damage in UR was weaker and occurred later than that in LR, which suggesting that OsMIOX may be involved in abiotic stress responses, and related to drought tolerance in plant[1].
  • The GUS activity was detected in spikelets, stem, leaves, especially in roots, and the activity was strongly induced by drought stress, indicating that OsMIOX was expressed in all rice organs and induced by drought stress. Overexpression of OsMIOX increases free proline contents under drought stress and increases the ROS-scavenging ability and decreases oxidative damage[1].
  • The third ranked gene is Os06g0561000. From the GO annotation, its function is inferred to participate in biological process as inositol catabolic process, L-ascorbic acid biosynthetic process and oxidation-reduction. Its corresponding protein is placed in cytoplasm by GO that has molecular function as iron ion binding, oxidoreductase activity, metal ion binding and inositol oxygenase activity. It is expressed as unnamed inositol oxygenase putatively[2][3].

Evolution

The ORF of OsMIOX obtained from UR variety, IRAT109, encodes a protein of 308 amino acids (aa). The BLAST analysis showed that the predicted amino acid sequence of the OsMIOX protein had high identity to other plant MIOX proteins, especially to Zea mays (87.99%), Vitis vinifera (75.56%) and Arabidopsis thaliana (74.28%), and had 43.69% identity to that from Homo sapiens, 41.42% identity to that from Sus scrofa[1].

Knowledge Extension

Figure 1. Functional roles of myo-inositol in plant metabolism.(from reference [4]).
  • Fig. 1 summarizes this information by categorizing specific products of myo-inositol (MI) metabolism with particular interest to plant biologists and by identifying avenues of inquiry which may lead to a better appreciation of this unique molecule and its position in plant science[4].
  • Colored backgrounds in Fig. 1 attempt to provide a sense of related functions while avoiding the confusion of ‘metabolic mapping’. Beyond its inhibitory effect on myo-inositol (MI) monophosphatase, little is known regarding its impact on availability of free myo-inositol (MI) for numerous biosynthetic and regulatory requirements (Fig. 1)[4].
  • Lithium ion delayed initiation of DNA synthesis and cell division when introduced into synchronized Catharanthus roseus cell cultures, a condition largely prevented when MI was included in the medium[4].

Labs working on this gene

  • Key Lab of Crop Heterosis and Utilization of Ministry of Education, Beijing Key Lab of Crop Genetic Improvement, China Agricultural University, Beijing 100193, PR China
  • International Rice Research Institute, Metro Manila, Philippines

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Duan J, Zhang M, Zhang H, et al. OsMIOX, a myo-inositol oxygenase gene, improves drought tolerance through scavenging of reactive oxygen species in rice (Oryza sativa L.)[J]. Plant Science, 2012, 196: 143-151.
  2. Wang J, Zhang F, Wang Y, et al. Identification of Salt Tolerance Genes in Rice from Microarray Data using SVM-RFE[C]//BICoB. 2011: 30-35.
  3. Tanaka T, Antonio B A, Kikuchi S, et al. The rice annotation project database (RAP-DB): 2008 update[J]. Nucleic acids research, 2008, 36(Supp 1): D1028-D1033.
  4. 4.0 4.1 4.2 4.3 Loewus F A, Murthy P P N. myo-Inositol metabolism in plants[J]. Plant Science, 2000, 150(1): 1-19.


Structured Information