Os07g0693800

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OsFAD8 is a putative rice chloroplast x-3 desaturase gene in rice[1].

Annotated Information

Function

OsFAD8, encoding a chloroplast x-3 fatty acid desaturase responsible for trienoic fatty acid formation[1]. Characterization of OsFAD8 suggests that it has a functional role in maintaining levels of trienoic fatty acids and stress tolerance at low temperatures[2].


GO assignment(s): GO:0006633,GO:0006636, GO:0016020, GO:0016491

Mutation

  • Two transgenic lines (8S-52 and 8S-101) harboring the Osfad8 ORF in sense orientation under the control of the CaMV 35S promoter contained increased levels of hexadecatrienoic (16:3) and linolenic (18:3) fatty acids. When exposed to 2 C for 7 days, the damage observed to the control plants was significantly alleviated in the 8S-52 and 8S- 101 lines. The amounts of trienoic fatty acids in an Osfad8 antisense line (8A-35) declined 40.2% compared to the control plants. The 8A-35 plants survived after growth at 44 C for 3 days while the control plants died[1].
  • OsFAD8 knockout mutants[2]:
    • Fatty acid analysis of homozygous OsFAD8 T-DNA knockout mutant and wild type plants have exhibited changes in fatty acid composition after cold stress, thus confirming that OsFAD8 gene codes for omega-3 fatty acid desaturase activity at low temperature.
    • Photosynthetic efficiency and recovery of OsFAD8 knockout mutants are significantly reduced after cold stress as compared to those of wild type plants.

Expression

  • Southern blot hybridization indicated that a small gene family composed of two copies or closely linked genes exists. RNA in situ hybridization showed that the accumulation of Osfad8 mRNA was abundant in leaves but hardly detectable in roots. The Osfad8 transcript level in leaves was much higher at 15°C than at normal temperature (25°C). In situ hybridization also showed particularly prominent expression of Osfad8 in the palisade layer and spongy parenchyma cells of leaves when exposed to 15°C conditions for 5 days and 10 days[1].
  • The Osfad8 gene was expressed highly in thylakoid rich photosynthetically active cell types, most notably in the palisade layers and spongy parenchyma cells, and was induced by moderate low temperature[1].
  • Transcript levels of OsFAD7 increased at high temperature; while those of OsFAD8 increased at low temperatures[2]. It was found that in the control treatments at 28 C, OsFAD7 expression was high, while OsFAD8 was less. However, the transcript level of OsFAD7 decreased with a decrease in temperature and that of OsFAD8 increased as a result of low temperature treatment, which showed that the OsFAD8 is a low-temperature inducible gene[2].

Subcellular localization

OsFAD7 and OsFAD8 localized in chloroplasts[3].

Evolution

Figure 1. A molecular phylogenetic tree of deduced amino acid sequences of Osfad8 from rice and the x-3 fatty acid desaturase from several other plant species.(from reference [1]).
  • Phylogenetic analysis using the deduced amino acid sequence of several plant x-3 desaturases is shown (Fig. 1). The x-3 fatty acid desaturase family includes representatives from a diverse group of plants, including both monocots and dicots. These representatives have been divided into three groups, which are related to their sequence and possibly function. OsFAD8 belongs to Group 2[1].
  • OsFAD8 is most closely related to TaFAD7 from wheat and shares approximately 81% identity. BLAST analysis showed that the deduced amino acid sequence of OsFAD8 has more than 80% similarity with those of FAD7 and FAD8. Rice x-3 desaturase gene is of high likelihood the homologous rice fad8 gene[1]. OsFAD7 having 78% similarity with OsFAD8, in the rice genome[2].

Labs working on this gene

  • Department of Biological Sciences, Pusan National University, Pusan, Republic of Korea
  • Institute of Genetics, State Key Laboratory of Genetic Engineering, Research Center of Gene Diversity and Designed Agriculture, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Science, Fudan University, Shanghai 200433, China
  • Faculty of Life Sciences, University of Manchester, 3.614 Stopford Building, Oxford Road, Manchester M13 9PT, UK

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Wang J, Ming F, Pittman J, et al. Characterization of a rice (Oryza sativa L.) gene encoding a temperature-dependent chloroplast ω-3 fatty acid desaturase[J]. Biochemical and biophysical research communications, 2006, 340(4): 1209-1216.
  2. 2.0 2.1 2.2 2.3 2.4 Nair P M G, Kang I S, Moon B Y, et al. Effects of low temperature stress on rice (Oryza sativa L.) plastid ω-3 desaturase gene, OsFAD8 and its functional analysis using T-DNA mutants[J]. Plant Cell, Tissue and Organ Culture (PCTOC), 2009, 98(1): 87-96.
  3. Yin Z J, Liu H L, Dong X, et al. Increasing α-linolenic acid content in rice bran by embryo-specific expression of ω3/Δ15-desaturase gene[J]. Molecular breeding, 2014, 33(4): 987-996.

Structured Information