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Genetic complementation analysis of rice sucrose transporter genes in Arabidopsis SUC2 mutant atsuc2
엄준섭,Cong Danh Nguyen,이대우,이상규,전종성 한국식물학회 2016 Journal of Plant Biology Vol.59 No.3
Sucrose transporters (SUTs) play a critical role on the phloem plasma membrane in loading sucrose into the phloem of source leaves for long-distance transport to sink organs. Rice has a small gene family of five SUTs, Oryza sativa SUT1 (OsSUT1) to OsSUT5. To identify rice SUTs that function as phloem loaders, we adopted a growth restoration assay of the severe growth retardation phenotype of atsuc2, a mutant of the best-characterized Arabidopsis phloem loader AtSUC2, by introducing OsSUTs. The rice SUT genes were expressed by two different promoters, the native phloem-specific promoter of AtSUC2 (pAtSUC2) and the constitutive Cauliflower Mosaic Virus 35S (pCaMV35S) promoter. Of all the transgenic atsuc2 plants, only pAtSUC2: OsSUT1 complemented the atsuc2 mutant phenotype in a comparable manner to wild type (WT), and consistent levels of soluble sugars and starch were recovered compared to those of WT. This suggests that OsSUT1 is a functional ortholog of the Arabidopsis AtSUC2 and functions as an apoplastic phloem loader. In addition, ossut1 mutants were produced via anther culture and their primary carbohydrate levels and growth phenotypes were indistinguishable from those of WT. This suggests that the rice phloem loader OsSUT1 function may not be essential for rice vegetative growth under normal conditions.
The Mechanism of Phloem Loading in Rice (Oryza sativa)
엄준섭,전종성,최상봉,John M. Ward 한국분자세포생물학회 2012 Molecules and cells Vol.33 No.5
Carbohydrates, mainly sucrose, that are synthesized in source organs are transported to sink organs to support growth and development. Phloem loading of sucrose is a crucial step that drives long-distance transport by eleva-ting hydrostatic pressure in the phloem. Three phloem loading strategies have been identified, two active mechanisms, apoplastic loading via sucrose transporters and symplastic polymer trapping, and one passive mechanism. The first two active loading mechanisms require metabolic energy, carbohydrate is loaded into the phloem against a concentration gradient. The passive process, diffusion, involves equilibration of sucrose and other metabolites between cells through plasmodesmata. Many higher plant species including Arabidopsis utilize the active loading mechanisms to increase carbohydrate in the phloem to higher concentrations than that in mesophyll cells. In contrast, recent data revealed that a large number of plants, especially woody species, load sucrose passively by maintaining a high concentration in mesophyll cells. However, it still remains to be determined how the worldwide important cereal crop, rice, loads sucrose into the phloem in source organs. Based on the literature and our results, we propose a potential strategy of phloem loading in rice. Elucidation of the phloem loading mechanism should improve our understanding of rice development and facilitate its manipulation towards the increase of crop productivity.
Expression and Functional Analysis of Rice Plastidic Maltose Transporter, OsMEX1
류나연,전종성,엄준섭,김현비,Bich Thuy Vo,이상원,한태룡 한국응용생명화학회 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.2
In Arabidopsis, maltose is a major product of the transitory starch degradation pathway at night, and its mobilization from the chloroplasts to the cytosol in leaf tissues via a plastidic maltose transporter, AtMEX1, is essential for normal plant growth. However, such a starch utilization pathway has not yet been characterized in rice (Oryza sativa), a monocot model plant. Examination of expression profiles of a rice plastidic maltose transporter, OsMEX1, by real-time polymerase chain reaction showed that it is abundant in the pollen grain-containing stamens of mature flowers. Consistently, high performance liquid chromatography analysis revealed a relatively high maltose content in mature flowers, suggesting that OsMEX1 mainly functions in the tissues. OsMEX1-green fluorescent protein fusion experiment confirmed that OsMEX1 localizes at the chloroplast envelope in both rice and Arabidopsis. Arabidopsis maltose excess1 (mex1) mutant was transformed with OsMEX1 fused to the cauliflower mosaic virus 35S (CaMV35S) promoter. In the resulting transgenic plants, the typical mutant phenotypes of Arabidopsis mex1, such as chlorosis, stunted growth, and maltose and starch deposition at the end of the night, are clearly rescued. This result demonstrates that OsMEX1 functions as a plastidic maltose transporter in Arabidopsis. Our present findings thus suggest that whereas the Arabidopsis MEX1 gene essentially functions in source leaf tissues, its rice counterpart likely has a role in the pollens of mature flowers.
RAHMAN MD MUSTAFIZUR,Rahman Md Mizanor,엄준섭,전종성 한국식물학회 2021 Journal of Plant Biology Vol.64 No.1
Trehalose-6-phosphate phosphatase (TPP) plays a key role in trehalose metabolism in plants. Here, we performed comprehensive in silico analyses and identified 12 OsTPPs (Oryza sativa TPPs) utilizing various bioinformatics tools. Phylogenetic tree, accomplished with OsTPPs and TPPs from 11 monocot and dicot species, was divided mainly into two clades, each clade containing six OsTPPs. Exon–intron distribution was related to phylogenetic clades. All OsTPPs are distributed within nine chromosomes (chr.), except Chr. 1, Chr. 5 and Chr. 11. OsTPPs were found to be stable in nature according to the 3-D structure prediction. Cis-regulatory elements (CREs) were also analyzed using 2 kb upstream of start codon for each gene to predict their biological functions. We categorized all CREs in five distinct groups based on core elements, stress response, cellular development, hormonal regulation, and unknown function, distributed in a range of 3–14 CREs in each group. Interestingly, our expression analysis showed that OsTPPs were more upregulated in response to drought and cold stresses compared to salt stress. Abundance of stress-related CREs found signifies TPPs’ possible role in stress response, which may facilitate to find related transcription factors and unveil complex molecular mechanisms during stress response.