The gene ''Os03g0125100'' (''LOC_Os03g03370'') was reported as '''''DSM2''''' in 2009. It encodes a '''putative BCH''' (named '''''DSM2'''''/'''''OsBCH1''''') belonging to the '''BCH family'''<ref name="ref1"/>. This gene was also named '''''OsHYD3'''''<ref name="ref2"/>.

==Annotated Information==
===Function===
The rice '''''DSM2''''' gene significantly contributes to control of the xanthophyll cycle and ABA synthesis, both of which play critical roles in the establishment of drought resistance in rice <ref name="ref1"/>. The functional analysis of the '''''DSM2''''' suggested that DSM2 is essential for drought resistance in rice.
<br><br>
'''GO assignment(s):''' [http://amigo.geneontology.org/amigo/term/GO:0003824 GO:0003824],[http://amigo.geneontology.org/amigo/term/GO:0008152 GO:0008152]
[[File:Os03g0125100-1.png|center|thumb|700px|'''Figure 1. Identification of dsm2 T-DNA insertion mutants and its drought sensitivity.'''<ref name="ref1" />]]

===Mutation===
* T-DNA insertion mutants in the background of japonica Zhonghua11 (ZH11) rice, selected from the Rice Mutant Database, for drought resistance under field conditions was screened by the researchers to identify critical genes required for drought resistance in rice. One of the drought-hypersensitive mutants showing drought sensitivity at both the seedling and panicle development stages, designated as ''dsm2-1'', was further characterized in this study.
====T-DNA Insertion Mutation====
* The T-DNA insertion sites of dsm2-1 and dsm2-2 are located in the third intron and the first exon, respectively.Under normal conditions, the homozygous mutants showed no obvious phenotypic change compared with the wild-type genotype segregated from the heterozygous mutant.
* To verify the drought-sensitive phenotype, mutant and wild-type plants at the four-leaf stage grown in sandy soil were subjected to drought stress. Under the moderate stress condition, the dsm2 mutant lines wilted faster than the wild type. After severe drought stress treatment followed by rewatering, almost all the mutant plants died, whereas wild-type plants had a significantly higher survival rate (Fig. 1C). Cosegregation analysis also suggested that the drought sensitivity was due to the T-DNA insertion in the OsBCH1 gene (data not shown). The dsm2-1 mutant was also more sensitive than the wild type to salt stress, but no significant difference was observed under cold or heat shock stress.
* Drought sensitivity of the dsm2-1 mutant was also tested at the reproductive stage by growing the mutant and the wild type in a paddy field facilitated with a removable rain-off shelter and in polyvinyl chloride (PVC) tubes filled with sandy soil. During the course of drought stress development, dsm2-1 showed wilting earlier than the wild type. After moderate drought stress in the PVC tubes, the total grain yield of dsm2-1 was reduced by about 52% compared with the wild type, and the pollen fertility of dsm2-1 (23%) was also significantly lower than that of the wild type (58%; Fig. 1D). The root depth and volume of dsm2-1 were significantly reduced compared with the wild type (Fig. 1D), and contents of chlorophyll and Pro in dsm2-1 were also reduced prominently.
====Overexpression of '''''DSM2'''''====
* To test whether DSM2 overexpression has a significant effect on improving drought resistance, the full-length cDNA of DSM2 under the control of the cauliflower mosaic virus 35S promoter (Fig. 2A) was transformed into japonica rice ZH11. After severe drought stress (no watering for 1 week), the overexpression lines had a significantly higher survival rate (approximately 74%) than the negative control (completely died; Fig. 2, C and D). After drought treatments at the reproductive stage, the overexpression lines had more green leaves and higher spikelet fertility than negative transgenic lines. The overexpression lines had less oxidative damage on the leaves and higher seed-setting rates than the negative control (Fig. 2, E and F). These results suggest that overexpression of DSM2 has a significant effect on the improvement of drought resistance in rice.

===Expression===
*Overexpression of ''DSM2'' in rice resulted in significantly '''increased resistance''' to '''drought''' and '''oxidative''' stresses and '''increases''' of the '''xanthophylls''' and '''nonphotochemical quenching'''. Some '''stress-related ABA responsive genes''' were '''up-regulated''' in the overexpression line<ref name="ref1"/>.

*Transcript analysis suggested that the expression of ''DSM2'' was abolished in the two allelic ''dsm2'' mutants. The ''DSM2'' transcript level was '''induced''' (7- to 9-fold) by '''drought''' and '''salt''' treatments and '''slightly''' induced by '''ABA'''. However, ''DSM2'' was '''not''' induced by the other treatments (and was '''slightly suppressed''' by '''cold''' stress)<ref name="ref1"/>.

*A '''strong GFP signal''' was observed in the '''stamen''', '''plumule''', '''hull''', '''pistil''','''mature leaf''', and '''root''', and a '''weak GFP signal''' was detected in '''calli''', '''young shoot''' and '''root''', and '''endosperm''', suggesting an organ/ tissue-dependent differential expression pattern of ''DSM2'' in rice<ref name="ref1"/>.

===Evolution===
In the rice genome, there are '''two homologs''' of ''DSM2''/ ''OsBCH1'', designated ''OsBCH2'' (LOC_Os04g48880) and ''OsBCH3'' (LOC_Os10g38940), showing '''82%''' and '''75% identity''' to ''OsBCH1'', respectively. ''DSM2'' belongs to the '''BCH family'''<ref name="ref1"/>.

==Knowledge Extension==
* Abiotic stresses such as drought, salinity, and adverse temperatures are major limiting factors for plant growth and reproduction. To respond to environmental cues, plants have evolved a variety of biochemical and physiological mechanisms to adapt to adverse conditions during their growth and development. Abscisic acid (ABA) has been recognized as a stress hormone that coordinates the complex networks of stress responses.
* Under drought or salt stress conditions, plant endogenous ABA level can rise to about 40-fold, triggering the closure of stomata and accumulating reactive oxygen species (ROS), dehydrins, and late embryogenesis abundant proteins for osmotic adjustment (Verslues et al., 2006). The endogenous ABA level is determined by ABA biosynthesis, catabolism, and release of ABA from ABA-Glc conjugates. Therefore, identification of all the components affecting active ABA content is essential for a complete understanding of the action of the hormone.

*The ''CYP97'' and ''BCH'' '''gene pairs''' are primarily responsible for hydroxylation of α- and β-carotenes, respectively, but exhibit some overlapping activities, most notably in hydroxylation of the β-ring of α-carotene. The BCH duplicates encode isozymes that show significant expression divergence in reproductive organs<ref name="ref3"/>.

*The two BCH isozymes could hydroxylate the β-ring of α-carotene, though again to a lower extent than the full four enzyme complement in the wild type<ref name="ref3"/>.

==Labs working on this gene==
*National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China

==References==
<references>
* <ref name="ref1">
Du H, Wang N, Cui F, et al. Characterization of the β-carotene hydroxylase gene DSM2 conferring drought and oxidative stress resistance by increasing xanthophylls and abscisic acid synthesis in rice[J]. Plant Physiology, 2010, 154(3): 1304-1318.
</ref>
* <ref name="ref2">
Vallabhaneni R, Gallagher C E, Licciardello N, et al. Metabolite sorting of a germplasm collection reveals the hydroxylase3 locus as a new target for maize provitamin A biofortification[J]. Plant physiology, 2009, 151(3): 1635-1645.
</ref>
* <ref name="ref3">
Kim J, Smith J J, Tian L, et al. The evolution and function of carotenoid hydroxylases in Arabidopsis[J]. Plant and cell physiology, 2009, 50(3): 463-479.
</ref>
</references>

==Structured Information==

[[Category:Genes]]
[[Category:Japonica mRNA]]
[[Category:Oryza Sativa Japonica Group]]
[[Category:Japonica Genes]]
[[Category:Japonica Chromosome 3]]
[[Category:Chromosome 3]]

File:Os03g0125100-3.png

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Xysj1990:

File:Os03g0125100-2.png

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2016-06-22T09:13:42Z

Xysj1990: /* The Background of This Project */

== Project Title ==
'''Microarray analysis of laser-microdissected tissues indicates the biosynthesis of suberin in the outer part of roots during formation of a barrier to radial oxygen loss in rice (Oryza sativa)'''

==The Background of This Project==
* Root growth into hypoxic or anoxic waterlogged substrates relies on internal diffusion of oxygen (Armstrong, 1979). The roots of waterlogging-tolerant species, such as rice (Oryza sativa), typically contain a large volume of aerenchyma. The aerenchyma provides a low-resistance pathway for diffusion of oxygen from the shoot base to the root tip (Armstrong, 1979). The roots of some wetland species, including rice, also possess a barrier to radial oxygen loss (ROL) within the basal zones (Armstrong, 1971; Visser et al., 2000; Colmer, 2003a; Garthwaite et al., 2003; Garthwaite et al., 2008; Abiko et al., 2012), so that ROL occurs predominately from short lateral roots (Armstrong and Armstrong, 2005) and the apical few centimetres of the main axes of adventitious roots (Fig. 1A). A barrier to ROL prevents loss of oxygen from the basal part of roots, which can enhance oxygen transport via the aerenchyma to the root tip. In the roots with an ROL barrier, oxygen at the root tip can be maintained at a higher level to allow root elongation into hypoxic/anoxic soil. The barrier might also impede entry of phytotoxins from chemically reduced water- logged soil.
* Another key feature contributing to waterlogging tolerance is aerenchyma formation. In rice roots, aerenchyma is formed constitutively, but the amount can be enhanced by soil water-logging (Armstrong, 1971; Pradhan et al., 1973; Jackson and Armstrong, 1999), low oxygen (Colmer et al., 2006), and ethylene (Justin and Armstrong, 1991; Colmer et al., 2006). On the other hand, the barrier to ROL is inducible in rice roots, forming in stagnant or waterlogged conditions, but not (or only weakly) in well-drained or aerated conditions (Colmer et al., 1998; Colmer, 2003a; Colmer et al., 2006; Insalud et al., 2006; Kotula et al., 2009; Shiono et al., 2011). Interestingly, low oxygen, ethylene, and elevated CO 2 , which arise from natural waterlogged soil, are not involved in triggering for- mation of the barrier to ROL in roots of rice (Colmer et al., 2006).
* The signal that triggers formation of the barrier to ROL is not known yet, but it may involve root exudates, cellular degradation products (Armstrong and Armstrong, 2001; Voesenek and Sasidharan, 2013) or phytotoxins present in chemically reduced waterlogged soils (e.g. Fe 2+ , sulphide, and microbial metabolites; Armstrong, 1979; Armstrong and Armstrong, 2005; Mongon et al., 2014). Aerenchyma and the barrier to ROL in roots are regarded as key features contrib- uting to long-distance oxygen transport and waterlogging tolerance in many wetland species (Armstrong, 1979; Jackson and Drew, 1984; Justin and Armstrong, 1987; Colmer, 2003b; Colmer and Voesenek, 2009; Nishiuchi et al., 2012). However, the molecular mechanism of ROL barrier formation is poorly understood (Shiono et al., 2008).

==Plant Materials & Treatment==
* Lowland rice (O. sativa L. cv. Nipponbare) was grown in a nutrient solution of the same composition as used in earlier studies of rice (Colmer, 2003a; Shiono et al., 2011). Plants were supported at the stem base in pots (light-shielding pots so roots were in darkness) within a controlled-environment chamber (24-h light, 28 °C, relative humidity over 50%, photosynthetic photon flux density at 214 μmol m –2 s –1 ). In each experiment, seeds were soaked for 30 min in 0.6% (w/v) sodium hypochlorite for surface sterilization. Seeds were then washed thoroughly with deionized water, and then the seeds were placed in Petri dishes containing about 5 mm deionized water for 2 d in darkness at 30 °C. After 2 d imbibition, germinated seeds were placed on stainless mesh floating on aerated quarter-strength nutrient solution and exposed to light. After 6 d imbibition, each seedling was held with soft sponge floating on aerated full-strength nutrient solution. After 9 d imbibition, seedlings were transferred to 5-l pots (height 250 mm, width 120 mm, breadth 180 mm) containing aerated full-strength nutrient solution. Solutions were renewed every 7 d.
* In each experiment, pots were arranged in a completely randomized design. 23-d-old plants were either continued in aerated solution or transplanted into N 2 -flushed or stagnant deoxygenated solution for 9 h (Fig. 1C). In N 2 -flushed nutrient solution, oxygen level was kept hypoxic (dissolved oxygen <1.0 mg l –1 ). Stagnant solution contained 0.1% (w/v) dissolved agar and was deoxygenated (dissolved oxygen <1.0 mg l –1 ) prior to use by preflushing with N 2 gas. The dilute agar prevents convective movements in solution (‘stagnant’ treatment) so this treatment mimics better than other solution culture methods the changes in gas composition found in waterlogged soils (e.g.
decreased oxygen, increased ethylene) (Wiengweera et al., 1997).
* Adventitious roots of 23-d-old plants were classified as short (65–85 mm) or long (115–135 mm), based on the length of the main axis at commencement of treatments. Selected short and long adventitious roots were marked near the base using small loops of sewing cotton, so these could be recognized over time.

== Labs working on this Project ==
* Department of Bioscience, Fukui Prefectural University, 4-1-1 Matsuoka-Kenjyojima, Eiheiji, Fukui 910-1195, Japan.
* Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan.
* Graduate School of Agriculture and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.
* Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore.
* School of Plant Biology and Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
* National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.
* Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, 1–308 Nonoichimachi, Ishikawa 921-8836, Japan.

==Corresponding Author==
'''Katsuhiro Shiono''' (email: shionok@fpu.ac.jp ) & '''Mikio Nakazono''' (email:nakazono@agr.nagoya-u.ac.jp)