（第１号様式の１）(Form # 1 （第３号様式）(Form No 3) 学 位 論 文 要 旨 Dissertation Abstract 氏名： Name Dan Quang Tran 学位論文題目： Title of Dissertation Studies on the halophilism in a halophyte,[.]
（第３号様式）(Form No 3) 学 位 論 文 要 旨 Dissertation Abstract 氏名： Name Dan Quang Tran 学位論文題目： Title of Dissertation Studies on the halophilism in a halophyte, the common ice plant, Mesembryanthemum crystallinum L (塩 生 植 物 ア イ ス プ ラ ン ト の 好 塩 性 に 関 す る 研 究 ) 学位論文要旨： Dissertation Abstract Salinit y is a serious environment al problem t hat reduces agricultural product ivit y Improvement of salt tolerance of crops and applicat ion of salt tolerant plant s as alt ernat ive crops are required to maintain stable and sust ainable agr icult ure product ion Halophyt es are salt-tolerant pla nt s t hat have abilit y to complet e their life cycle under high salinit y Some of halophytes also require salt at some ext ent s for t heir maximum growt h, which is important trait for t he salt adapt at ion of halophyt e and referred to as halophilism To elucidat e t he mechanisms of halophilism, t he effect s of NaCl on fact ors relat ed to cell growt h such as cell elongat ion, cell division, and ATP synt hesis were examined on a halophyt e, t he common ice plant (Mesembryanthenum crystallinum L.) Expression of ion homeostasis related genes associated with salt-stimulated cell elongation The salt-st imulat ed cell elongat ion and accumulat ion of ions K + , Na + , NO − and Cl − in t he suspension cult ured M crystallinum cells grown under 100 mM NaCl condit ion have been observed in a previous study in our laboratory, suggest ing t hat t he cells may regulat e io n ho meostasis and osmot ic adjust ment for enhancing t he cell elongat ion In t he present study, t he factors t hat are induced by NaCl to promote t he cell elongat ion and t he mechanism of salt-st imulat ed cell elongat ion were elucidat ed The growt h of cells in cult ure medium contained 100 mM NaCl was higher t han that in t he medium contained PEG wit h t he equivalent osmot ic pressure, suggest ing t hat the growth enhancement was due to the ionic effect more t han osmot ic effect of NaCl Genes for Cl - ho meost asis, which encode a plasma membrane cat ion/Cl cotransporter (McCCC1) and a tonoplast Cl - /H + ant iport er (McCLC1), were annotated using t he cDNA database of t he ice plant In addit ion, the expression analysis of genes encoding plasma membrane transporters and channels for incorporat ion of Na + (McHKT1), Cl − (McCCC1), NO − (McNRT1), K + (McHAK1, McKmt1), and wat er (McMipC); tonoplast transport er s for vacuolar sequestrat ion of Cl − (McCLC1), Na + (McNHX1), and V-ATPase subunit c (McVmac1); and enzymes for synt hesis of proline (McP5CS), ononitol (McImt1), and cell wall met abolis m xyloglucan endotransglucosylase/hydrolase (McXTH) in t he cells treated wit h 100 mM NaCl showed t hat t he expression of McHKT1, McCCC1, McCLC1, McNHX1, McVmac1, McKmt1, McNRT1, McP5CS, and McImt1 were higher in t he salt treated cells t han t hat in t he u ntreat ed cells The result s suggested t hat these genes were invo lved in t he accumulat ion of ions and compat ible solut es, which might contr ibute to the enhancement of turgor pressure and cell elongat ion in t he ice plant cells grown posit ively wit h NaCl （第３号様式）(Form No 3) Expression of cell cycle related genes associated with salt-stimulated cell division The previous study also showed t hat t he enhancement of cell division contribut ed to the halophilism of t he ice plant To elucidate the factors associat ed wit h t he salt-st imulat ed cell division, in t he present study, t he G1-S phase synchronized suspension cells were produced by phosphat e st arvat ion for 72 h, and t he expression of cell cycle relat ed genes was analyzed on the synchronized cells grown posit ively with 25 mM NaCl In addit ion, fift een cell cycle relat ed genes t hat are associat ed wit h t he regulat ion of progression of G1 phase (McCycD2;1, McKRP2/ICK2, McCDKA;1, and McCycD3;1), S phase (McHistone H4, McKRP3, McCKS1At, McE2Fb, and McCDKA;1), G2 phase (McCDKB1;1, McKRP4, McCycD1;1, McCycB2;1, and McCDKA;1), and M phase (McCDKB2;2, McCycA2;1, McCycB1;1, McCycD3;1, McCDKA;1, and McCKS1At) were annotated using the cDNA database of t he ice plant Using t he synchronized cells, t he expression analysis of McCycD2;1, McCycD3;1, McHistone H4, and McKRP3 showed t hat t he expression of McCycD2;1, McCycD3;1 were higher in t he salt treated cells t han t hat in t he unt reated cells, suggest ing t hat NaCl might promote t he progression of G1 phase t hat contribut ed to the salt -st imulat ion cell division Expression of mitochondrial ATP synthesis related genes associated with salt-stimulated ATP synthesis The ATP synt hesis is considered to increase to meet the increased energy demand of halophilism of t he ice plant In t he present study, stat ist ical analysis on t he data of ATP synt hesis obt ained in t he previous study, which measured the ATP synt hesis rate in mitochondr ia iso lat ed from t he ice plant s grown wit h 0, 100, 400 mM NaCl in the assay mixt ures cont ained 50-350 mM NaCl wit h fixed MPa osmot ic pressure, showed t hat the ATP synt hesis increased wit h increasing NaCl concentrat ions , up to 350 mM, in t he assay mixt ures In addit ion, t he ATP synt hesis rate was higher in mitochondr ia isolat ed from t he plant grown wit h NaCl t han t hat of t he plant grown wit hout NaC l These result s suggested that NaCl st imulat es t he ATP synt hesis, which contr ibute s to the halophilism of t he ice plant To elucidate the factors invo lved in salt-st imulat ed ATP synt hesis, nine genes encoding mitochondr ial ATP synt hesis related proteins such as a bet a subunit of ATP synt hase ( McATPF1b); subunit s o f elect ron transport chain (ETC) complexes such as a 76 kDa subunit of complex I (McCI76), flavoprotein subunit of complex II ( McSDH1-1), 6B subunit of complex III (McCOX6B-1), subunit of complex IV (McQCR7) and alt ernat ive oxidase (McAOX1a); subunit s of tricarboxylic acid (TCA) cycle relat ed enzymes such as an E1 alpha subunit of pyruvate dehydrogenase (McPDHE1α) and malat e dehydrogenase ( McmMDH1); and mitochondrial phosphate transporter (McMPT1) were annotated using t he cDNA database of t he ice plant The expression of t hese genes and adenylate transport er McANT2 were analyzed on t he suspension cultured cells grown posit ively wit h 100 mM NaCl The expression of McATPF1b, McCOX6B-1, McCI76, McQCR7, McSDH1-1, McmMDH1, McPDHE1α, and McANT2 was higher, but t he expression of McAOX1a was lower in t he salt treated cells t han t hat in t he unt reat ed cells These result s suggested t hat McATPF1b, McCOX6B-1, McCI76, McQCR7, McSDH1-1, McmMDH1, McPDHE1α, McANT2, McAOX1a were involved in t he salt-st imulat ed ATP synt hesis It also suggested t hat t he ATP synt hase, ETC, and TCA might be promot ed by salt to enhance t he ATP synt hesis