Caffeine biosynthesis and adenine metabolism in transgenic Coffea canephora plants with reduced expression of N-methyltransferase genes.
In anti-sense and RNA interference transgenic plants of Coffea canephora in which the expression of CaMXMT1 was suppressed, caffeine biosynthesis from [8-(14)C]adenine was investigated, together with the overall metabolism of [8-(14)C]adenine. Compared with wild type control plants, total purine alkaloid biosynthesis from adenine and conversion of theobromine to caffeine were both reduced in the transgenic plants. As found previously, [8-(14)C]adenine was metabolised to salvage products (nucleotides and RNA), to degradation products (ureides and CO(2)) and to purine alkaloids (theobromine and caffeine). In the transgenic plants, metabolism of [8-(14)C]adenine shifted from purine alkaloid synthesis to purine catabolism or salvage for nucleotides. HPLC analysis revealed a significantly reduced caffeine content in the transgenic plants. A small quantity (less than 20 nmol g(-1) fresh weight) of xanthosine had accumulated in at least one of the transgenic plants.
Ashihara
Hiroshi
H
Metabolic Biology Group, Department of Biology, Faculty of Science, Ochanomizu University, Bunkyo-ku, Tokyo, Japan. ashihara@cc.ocha.ac.jp
Zheng
Xin-Qiang
XQ
Katahira
Riko
R
Morimoto
Masayuki
M
Ogita
Shinjiro
S
Sano
Hiroshi
H
D000225:Adenine / Q000378:metabolism*; D002110:Caffeine / Q000096:biosynthesis*; D002851:Chromatography, High Pressure Liquid; D040503:Coffea / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D030821:Plants, Genetically Modified
D002110:Caffeine; D008780:Methyltransferases; D000225:Adenine