Systematic identification of X1-homologous genes reveals a family involved in stress responses in rice
X1-homologous genes (XHS) encode plant-specific proteins containing three major domains (XH, XS, zf-XS), but their functions are largely unknown. We report the systematic identification and characterization of XHS genes in the rice genome. Eleven putative XHS protein sequences (OXHS1–11) were identified in the sequenced genome of Oryza sativa japonica cv. Nipponbare, and these sequences, along with other plant XHS homologues, were classified into five subgroups based on phylogenetic analysis. Distinct diversification of the XHS proteins occurred between monocotyledon and dicotyledon plants. The OXHS family has diverse exon–intron structures and organizations of putative domains and motifs. The OXHS proteins showed no transactivation activity, and no interaction between the XH domain and the XS domain in yeast. Four representative OXHS proteins were targeted to cytoplasm, which contradicts the previous speculation that XHS proteins are putative transcription factors. All the OXHS genes are predominantly expressed in floral organs, and some are expressed in a wide range of tissues or organs in indica rice Minghui 63. Nine OXHS genes are responsive to at least one of the abiotic stresses including drought, salt, cold, and abscisic acid treatment. Over-expression of one stress-responsive gene OXHS2 in rice resulted in reduced tolerance to salt and drought stresses. These results suggest that the OXHS family may be functionally diversified and some members of this family may play important roles in regulating stress tolerance in rice.
KeywordsOryza XHS family Abiotic stress Over-expression
XH and XS domain
Polymerase chain reaction
This work was supported by grants from the National Special Key Project of China on Functional Genomics of Major Plants and Animals, the National Natural Science Foundation of China, and the Ministry of Education of China.
- Huala E, Dickerman AW, Garcia-Hernandez M, Weems D, Reiser L, LaFond F, Hanley D, Kiphart D, Zhuang M, Huang W, Mueller LA, Bhattacharyya D, Bhaya D, Sobral BW, Beavis W, Meinke DW, Town CD, Somerville C, Rhee SY (2001) The Arabidopsis Information Resource (TAIR): a comprehensive database and web-based information retrieval, analysis, and visualization system for a model plant. Nucleic Acids Res 29:102–105CrossRefPubMedGoogle Scholar
- Jain M, Nijhawan A, Arora R, Agarwal P, Ray S, Sharma P, Kapoor S, Tyagi AK, Khurana JP (2007) F-box proteins in rice. Genome-wide analysis, classification, temporal and spatial gene expression during panicle and seed development, and regulation by light and abiotic stress. Plant Physiol 143:1467–1483CrossRefPubMedGoogle Scholar
- Kikuchi S, Satoh K, Nagata T, Kawagashira N, Doi K, Kishimoto N, Yazaki J, Ishikawa M, Yamada H, Ooka H, Hotta I, Kojima K, Namiki T, Ohneda E, Yahagi W, Suzuki K, Li CJ, Ohtsuki K, Shishiki T, Otomo Y, Murakami K, Iida Y, Sugano S, Fujimura T, Suzuki Y, Tsunoda Y, Kurosaki T, Kodama T, Masuda H, Kobayashi M, Xie Q, Lu M, Narikawa R, Sugiyama A, Mizuno K, Yokomizo S, Niikura J, Ikeda R, Ishibiki J, Kawamata M, Yoshimura A, Miura J, Kusumegi T, Oka M, Ryu R, Ueda M, Matsubara K, Kawai J, Carninci P, Adachi J, Aizawa K, Arakawa T, Fukuda S, Hara A, Hashizume W, Hayatsu N, Imotani K, Ishii Y, Itoh M, Kagawa I, Kondo S, Konno H, Miyazaki A, Osato N, Ota Y, Saito R, Sasaki D, Sato K, Shibata K, Shinagawa A, Shiraki T, Yoshino M, Hayashizaki Y, Yasunishi A (2003) Collection, mapping, and annotation of over 28, 000 cDNA clones from japonica rice. Science 301:376–379CrossRefPubMedGoogle Scholar
- Koiwa H, Barb AW, Xiong L, Li F, McCully MG, Lee BH, Sokolchik I, Zhu J, Gong Z, Reddy M, Sharkhuu A, Manabe Y, Yokoi S, Zhu JK, Bressan RA, Hasegawa PM (2002) C-terminal domain phosphatase-like family members (AtCPLs) differentially regulate Arabidopsis thaliana abiotic stress signaling, growth, and development. Proc Natl Acad Sci U S A 99:10893–10898CrossRefPubMedGoogle Scholar
- Mourrain P, Beclin C, Elmayan T, Feuerbach F, Godon C, Morel JB, Jouette D, Lacombe AM, Nikic S, Picault N, Remoue K, Sanial M, Vo TA, Vaucheret H (2000) Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance. Cell 101:533–542CrossRefPubMedGoogle Scholar