Os11g0167800

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Annotated Information

Function

Among cereal crops, rice is considered the most tolerant toaluminium (Al). However, variability among rice genotypes leads to remarkable differences in the degree of Al tolerance for distinct cultivars. A number of studies have demonstrated that rice plants achieve Al tolerance through an unknown mechanism that is independent of root tip Al exclusion. We have analysed expression changes of the rice ASRgene family as a function of Al treatment. The gene ASR5was differentially regulated in the Al-tolerant ricessp. Japonica cv. Nipponbare. However,ASR expression did not respond to Al exposure in Indica cv. Taim rice roots,which are highly Al sensitive. Transgenic plants carrying RNAi constructs that targeted theASRgenes wereobtained, and increased Al susceptibility was observed in T1 plants. Embryogenic calli of transgenic rice carrying an ASR5-green fluorescent protein fusion revealed that ASR5 was localized in both the nucleus and cytoplasm. Using a proteomic approach to compare non-transformed and ASR-RNAi plants, a total of 41 proteins with contrasting expression patterns were identified. We suggest that the ASR5 protein acts as a transcription factor to regulate the expression of different genes that collectively protect rice cells from Al-induced stress responses.

Expression

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   Aluminium (Al) is the most abundant metal, accounting for approximately 7% of Earth’s mass. Regardless of its abundance,Al is not considered an essential nutrient; however, it can occasionally stimulate plant growth or induce other desirable effects when present atlow concentrations (Foy1983). Most Al is chelated by ligands or is present in non-toxic forms, such as aluminosilicates or precipitates. Al-induced toxicity can occur through solubilization of Al in soils under highly acidic conditions (pH below 5.0)(Famoso et al. 2010). It has been estimated that approximately 50% of arable land is negatively impacted by Al toxicity that results from acidic soil(Panda,Baluska&Matsumoto 2009). Al toxicity is considered a primary limiting factor in regard to agricultural productivity (Matsumoto 2000) because it inhibits root growth and mineral absorption (Liu & Luan 2001), leading to a stunted root system that negatively impacts the uptake of water and nutrients.There are many potential cellular locations that could be damaged through interaction with Al, including the cell wall, the surface of the plasma membrane, the cytoskeleton and the nucleus (Pandaet al. 2009). For example, it has been demonstrated that Al binds strongly to the cell wall of root epidermal and cortical cells (Delhaize, Ryan & Randall1993). However, some plants are able to tolerate toxic levels of Al in acidic soils. These plants have evolved mechanisms to detoxify Al that is both present internally and externally(Kochian, Pineros & Hoekenga 2005). To achieve internal detoxification, plants accumulate Al inside vacuoles, where it is chelated with organic acids (OA), such as citrate and oxalate (Ma 2007). In contrast, the majority of Al-tolerant plants exclude Al from the root tip by releasing OA at sites of high Al concentration; examples of these acids include malate, citrate and oxalate (Ma, Ryan & Delhaize 2001; Kochian, Hoekenga & Pineros 2004). In species such as sorghum and wheat, the OA–Al complex prevents Al from entering the cell (Sasakiet al. 2004; Magalhaes et al. 2007),which reduces the concentration and potential toxicity of Al at the growing root tip (Ma et al. 2001). 
   Rice is considered the most Al-tolerant crop (Fageria1989; Duncan & Baligar 1990); however, there is variability among different rice genotypes, resulting in widely varied tolerance levels among different cultivars (Ferreira 1995).In two independent studies, Ma et al. (2002) and Yang et al.(2008) observed no OA exudation and increased Al accumulation in the root apex of Al-susceptible rice strains relative to Al-tolerant strains. These results demonstrate that rice plants achieve high levels of Al tolerance through anovel mechanism that does not involve root tip Al exclusion(Famosoet al. 2010). Although genetic studies in rice have identified more than 10 quantitative trait loci for Al tolerance, the responsible genes have only recently been cloned (Huang et al. 2009). The genes STAR1andSTAR2were isolated from an Al-tolerant cultivar irradiated withg-rays (Ma et al.2005). The disruption of either gene resulted in hypersensitivity to Al toxicity. STAR1encodes a nucleotide-bindingdomain protein, and STAR2 encodes a transmembrane domain protein of a bacterial-type ATP-binding cassette (ABC) transporter. Analyses indicated that STAR1 and STAR2form a complex that functions as an ABC transporter that is required for detoxification of Al in rice. The ABC transporter transports uridine diphosphate (UDP)-glucose, which may be used to modify the cell wall (Huanget al. 2009). Yamajiet al. (2009) isolated the zinc finger transcription factor ART1, which regulates multiple rice genes implicated in Al tolerance. Genes regulated by ART1 include STAR1, STAR2andNrat1, the latter of which is a specific transporter that mediates the sequestration of trivalent Al ions into vacuoles to achieve Al detoxification (Xia et al. 2010).
   Using a proteomic approach, Yanget al. (2007) identified some proteins responsive to Al in rice roots; ASR5 was more highly expressed in these roots. TheASR(abscisic acid, stress and ripening) gene was first described in tomato(Iusemet al. 1993). Subsequently,ASRgenes were found to be widely distributed in the vegetal kingdom, having been identified in potato (Silhavyet al. 1995), pinus (Chang et al. 1996), maize (Riccardi et al. 1998), rice (Vaidyanathan,Kuruvila & Thomas 1999), sugarcane (Sugihartoet al. 2002),grape (Cakir et al. 2003) and others. Nevertheless, ASR genes do not occur in the genome ofArabidopsis thaliana(Maskinet al. 2001). ASRgenes are expressed during fruit ripening and are induced in response to ABA and various abiotic stresses, including water and salt stresses (Carrari,Fernie & Iusem 2004). Kalifaet al. (2004a) demonstrated that tomato ASR1 proteins were present as unstructured monomers localized in the cytosol and as structured homodimers in the nucleus, where they can bind DNA.Cytosolic tomato ASR1 performs a chaperone-like activityand can stabilize a number of proteins, protecting them from denaturation induced by repeated freeze/thaw cycles(Konrad & Bar-Zvi 2008). Furthermore, a grape ASR protein binds to the promoter of a hexose transporter gene(Cakiret al. 2003), suggesting that it may be a transcription factor that is involved in sugar metabolism.In silicoanalyses mapped the locations of six copies ofASRgenes in the rice genome in different chromosomes; these loci were confirmed by expressed sequence tags (ESTs) (Frankel et al.2006). 
   In this study, we analysed changes in gene expression of the riceASRfamily in response to Al treatment. We found that all members of the ASRgene family display a variable degree of expression, indicating thatASRgenes of the tolerant Japonica rice (cv. Nipponbare) are differentially regulated in response to Al. Conversely,ASR5did not respond to Al exposure in Indica rice roots (cv. Taim), which unlike the Nipponbare cultivar, is highly sensitive to Al (Freitas et al. 2006).According to Maet al. (2002), Japonica varieties are often more resistant to Al than the Indica varieties. Inaddition to gene expression analyses, transgenic plants carrying RNAi constructs targeting theASRgenes were made,and an increased Al susceptibility was observed in T1 plants. In addition, transgenic embryogenic calli of rice carrying an ASR5-green fluorescent protein (GFP) fusion protein revealed that ASR5 is located in both the nucleus and the cytoplasm, suggesting that ASR5 may act as a transcription factor.

Evolution

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Labs working on this gene

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References

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Structured Information

Gene Name	Os11g0167800
Description	Similar to Anth (Pollen-specific desiccation-associated LLA23 protein)
Version	NM_001072373.1 GI:115484358 GeneID:4349876
Length	969 bp
Definition	Oryza sativa Japonica Group Os11g0167800, complete gene.
Source	Oryza sativa Japonica Group ORGANISM Oryza sativa Japonica Group Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta; Spermatophyta; Magnoliophyta; Liliopsida; Poales; Poaceae; BEP clade; Ehrhartoideae; Oryzeae; Oryza.
Chromosome	Chromosome 11
Location	Chromosome 11:3261662..3262630
Sequence Coding Region	3262004..3262189,3262309..3262539
Expression	GEO Profiles:Os11g0167800
Genome Context	<gbrowseImage1> name=NC_008404:3261662..3262630 source=RiceChromosome11 preset=GeneLocation </gbrowseImage1>
Gene Structure	<gbrowseImage2> name=NC_008404:3261662..3262630 source=RiceChromosome11 preset=GeneLocation </gbrowseImage2>
Coding Sequence	<cdnaseq>atggcggaggagaagcaccaccaccacctgttccaccacaagaaggacgacgagccggccaccggagtagactcctacggcgagggcgtctacacgtcggagacggtgaccaccgaggtggtcgccggcggccaggacgagtacgagaggtacaagaaggaggagaagcagcacaagcacaagcagcacctcggcgaggccggcgccctcgccgccggcgccttcgccctgtatgagaagcacgaggcgaagaaggacccggagaacgcgcacaggcacaagatcacggaggagatcgcggccacggcggcggtcggcgccggcggctacgccttccacgagcaccacgagaagaagaaggaccacaagagcgccgaggagtccaccggcgagaagaagcaccacctcttcggctga</cdnaseq>
Protein Sequence	<aaseq>MAEEKHHHHLFHHKKDDEPATGVDSYGEGVYTSETVTTEVVAGG QDEYERYKKEEKQHKHKQHLGEAGALAAGAFALYEKHEAKKDPENAHRHKITEEIAAT AAVGAGGYAFHEHHEKKKDHKSAEESTGEKKHHLFG</aaseq>
Gene Sequence	<dnaseqindica>442..627#92..322#aagcaagcaaagccacatcttattgtcacttccatctcattctcctaattgtcatcactagcttctagctagcttaattaattaattagccatggcggaggagaagcaccaccaccacctgttccaccacaagaaggacgacgagccggccaccggagtagactcctacggcgagggcgtctacacgtcggagacggtgaccaccgaggtggtcgccggcggccaggacgagtacgagaggtacaagaaggaggagaagcagcacaagcacaagcagcacctcggcgaggccggcgccctcgccgccggcgccttcgccctggtaattaactaattaattaaccactaattaattgatctaacgccgccttaattaatcaattaatttgctaagaaatcatcaagaagtaattaattaagctgattaatcgtggtgtgtagtatgagaagcacgaggcgaagaaggacccggagaacgcgcacaggcacaagatcacggaggagatcgcggccacggcggcggtcggcgccggcggctacgccttccacgagcaccacgagaagaagaaggaccacaagagcgccgaggagtccaccggcgagaagaagcaccacctcttcggctgatcgacctcatcacaacgtcgccggcggcggcgacgacctcgccgtacgtcgccggccgccgtgtcgtcgatttgtgtgtgtaataatttgtcttcttctgcatgcgtggtgttgctgtttttcacaagagtctccggcctcgaccagtgagaggctgacaggtggggccgtgagttcagcttgtgttgcttgattttctctgcagccttgccctctgtgtgtccaaataagtggtgtgcatggctctctccgtgtcatgtatcaatgtatttttatctgtactttgtacaagtgaagcaatatttatcgaaccttgactttctccattctatttgaaaaacc</dnaseqindica>
External Link(s)	NCBI Gene:Os11g0167800, RefSeq:Os11g0167800