Ο μεταβολισμός του άνθρακα στον καρπό της τομάτας ; Carbon metabolism in tomato fruit

Carbon metabolism in tomato fruit is highly dependent on carbon influx, aswell as CO2 contribution. It is well established that CO2 inside fruit is plentiful.The key enzyme of converting CO2 to bicarbonate is cabonic anhydrase (CA).For this reason, CA activity and immunohistolocalization was studied throughouttomato fruit tissues. In addition, the expression pattern of three alreadycharacterized CA isozymes LeCA1, LeCA2, LeCA3 was studied in all tomatotissues during day as well as in tomato fruit tissues, specifically, during day andnight. In daytime, the mature green fruit is able for photosynthesis, though atminimal rates, through Rubisco. During night, however, the enzyme responsiblefor CO2 recapturing is PEPC. This was the reason for the studying of PEPCactivity, protein and transcripts as well as PEPCk gene expression pattern in adiel cycle. There is evidence that PEPC is active during night, thus,incorporating CO2 into malate and/or citrate. Followingly, the concentrations ofmalic and citric acid, that account for the bulk of organic acids in tomato fruitwas examined. Both metabolites had the highest accumulation during day at13:00, while the minimum was recorded at 03:00. There were also studiedsome of the enzymes that correlate with malate and citrate metabolism, such asthe two isoforms of malate dehydrogenases (NADP-MDH), malic enzymes(NADP-ME), the isoforms of citrate synthases, the pyruvate orthophosphatedikinase, the triose phosphate transporter and the circadian-related gene. Someof the previous mentioned genes are C4 related. Moreover, it is suggested thatthe three tomato tissues adopt a different kind of metabolism and the fate ofmalate and citrate during night is discussed. This is the first time that certaingene expression patterns are studied diurnally, as well as it is the firstquantitative experiment evaluating concentrations and accumulation of malateand citrate in tomato fruit tissues. ; Ο μεταβολισμός του άνθρακα στον καρπό της τομάτας εξαρτάται σε μεγάλοβαθμό από τις εισροές του άνθρακα ...