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OsCIN1 has a critical role during the pre-storage phase, being involved in the proliferation of endosperm cells and longitudinal growth of immature seeds, rather than during the starch-filling phase.
OsCIN1, a rice CIN gene, is active in developing seeds. OsCIN1 has a critical role during the pre-storage phase, being involved in the proliferation of endosperm cells and longitudinal growth of immature seeds, rather than during the starch-filling phase.Cell-wall invertase (CIN) catalyzes the hydrolysis of sucrose into glucose and fructose for the supply of carbohydrates to sink organs via an apoplastic pathway.CINs are most active in the apoplast of sink organs,and can be involved in sucrose partitioning, control of cell differentiation and plant development, and responses to wounding and pathogen infection. The cDNA, designated OsCIN1, contains an open reading frame of 1731 bp encoding a polypeptide of 577 amino acid residues. The deduced amino acid sequence showed typical features of the cell wall invertases, including a β-fructosidase motif and a cysteine catalytic site, and shared 78.6 and 73.7% identity with maize cell wall invertases, Incw1 and Incw2, respectively.
ExpressionOsCIN1 transcript is detectable only in the very early stage of their development, 1-4 d after flowering, when the cell wall invertase activity is the highest and the increase in caryopsis length is rapid. In situ localization of the mRNA revealed that OsCIN1 is expressed preferentially in the vascular parenchyma of the dorsal vein, integument and its surrounding cells, and is expressed weakly in the nucellar projection and nucellar epidermis.
OsCIN1 was highly expressed in the ovary and at the veryearly developmental stage of the seed (1–2 DAF). Levels of OsCIN1 transcript dramatically decreased during 5–8 DAF and were weak thereafter.Drought stress near heading reduces grain yield in rice cultivars by inhibiting processes such as anther dehiscence and panicle exsertion. Because cell-wall invertases play an important role in carbon allocation to developing organs, we examined the tissue-specific expression and drought sensitivity of the corresponding genes (OsCIN1-9) at heading in the widely grown cultivar IR64. OsCIN1-5,8 were expressed to varying degrees in flag leaf, panicle, anthers and peduncle at 1 day before heading (1 DBH). When water was withheld for 2 days starting 3 DBH, anthesis and peduncle elongation were halted. At the same time, transcript levels for OsCIN1-5,8 genes were all markedly down-regulated in anthers and/or peduncles but were not affected in flag leaves. Re-watering allowed anthesis and peduncle elongation to proceed and restored expression of OsCIN1-5,8.
EvolutionRice genome has a CWI family consisting of eight members. Our previous study has demonstrated that GIF1 is a member of the gene family and required for assimilated carbon partitioning during early grain-filling. A phylogenetic analysis of the known plant CWI genes and predicted CWI genes from the recently released maize and sorghum genomes showed that OsCIN1, located on chromosome 2, is highly similar to GIF1 located on chromosome 4. Genetic distance based on amino acid substitutions also indicated that OsCIN1 is most closely related to GIF1. To gain insight into their evolutionary relationship, the 500-kb flanking sequences of the GIF1 and OsCIN1 regions were compared. The other eight expressed genes flanking the GIF1 gene on chromosome 4 show good colinearity to the eight counterparts of the OsCIN1 region on chromosome 2. The result indicated that GIF1 and OsCIN1 rose via duplication of a genomic block, which could be as large as 15 Mb (data not shown).Phylogenetic analysis including cell-wall invertases of Zea mays, Sorghum bicolor, Lolium perenne, Hordeum vulgare, Dendrocalamopsis oldhamii and Oryza sativa showed that GIF1 was closer to cell-wall invertases of Zea mays, Hordeum vulgare and Dendrocalamopsis oldhamii, suggesting that this duplication might occur during the genome duplication of grasses. By directly using synonymous substitution rate between the two paralogs (Ks = 0.57), and assuming the neutral evolutionary rate of rice genes (~6.5 × 10-9substitutions per silent site per year), we estimated the time of duplication between GIF1 and OsCIN1 about 44 million years ago (MYA), a time much earlier than the genus Oryza diversified from a common ancestor about 15 MYA . However, this estimated duplication age could be invalid because the regions were likely selected during rice domestication.
Labs working on this gene
1. Natl Agr Res Ctr, Dept Rice Res, Niigata 9430193, Japan. 2. Natl Inst Agrobiol Sci, Dept Plant Physiol, Tsukuba, Ibaraki 3058602, Japan. 3. Chinese Acad Sci, Natl Lab Plant Mol Genet, Inst Plant Physiol & Ecol, Shanghai Inst Biol Sci, Shanghai 200032, Peoples R China. 4. Int Rice Res Inst, Plant Breeding Genet & Biochem Div, DAPO Box 7777, Manila, Philippines. 5. Kyung Hee Univ, Plant Metab Res Ctr, Suwon 449701, South Korea.
- Cho JI, Lee SK, Ko S, Kim HK, Jun SH, Lee YH, Bhoo SH, Lee KW, An G, Hahn TR, Jeon JS.Molecular cloning and expression analysis of the cell-wall invertase gene family in rice (Oryza sativa L.).Plant Cell Rep. 2005 Jun;24(4):225-36.
- Hirose T, Takano M, Terao T.Cell wall invertase in developing rice caryopsis: molecular cloning of OsCIN1 and analysis of its expression in relation to its role in grain filling.Plant Cell Physiol. 2002 Apr;43(4):452-9.
- Ji XM, Raveendran M, Oane R, Ismail A, Lafitte R, Bruskiewich R, Cheng SH, Bennett J.Tissue-specific expression and drought responsiveness of cell-wall invertase genes of rice at flowering.Plant Mol Biol. 2005 Dec;59(6):945-64.
- Ertao Wang, Xun Xu, Lin Zhang, Hong Zhang, Lin Lin, Qin Wang, Qun Li, Song Ge, Bao-Rong Lu, Wen Wang, and Zuhua He.Duplication and independent selection of cell-wall invertase genes GIF1 and OsCIN1 during rice evolution and domestication.BMC Evol Biol. 2010; 10: 108.