STRESS RESPONSES IN ALFALFA (MEDICAGO-SATIVA L) .19. TRANSCRIPTIONAL ACTIVATION OF OXIDATIVE PENTOSE-PHOSPHATE PATHWAY GENES AT THE ONSET OF THE ISOFLAVONOID PHYTOALEXIN RESPONSE

被引:67
作者
FAHRENDORF, T [1 ]
NI, WT [1 ]
SHORROSH, BS [1 ]
DIXON, RA [1 ]
机构
[1] SAMUEL ROBERTS NOBLE FDN INC,DIV PLANT BIOL,ARDMORE,OK 73401
关键词
ALFALFA; ELICITATION; GLUCOSE 6-PHOSPHATE DEHYDROGENASE; ISOFLAVONOIDS; PENTOSE PHOSPHATE PATHWAY; 6-PHOSPHOGLUCONATE DEHYDROGENASE;
D O I
10.1007/BF00042073
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We have isolated cDNA clones encoding the pentose phosphate pathway enzymes 6-phosphogluconate dehydrogenase (6PGDH, EC 1.1.1.44) and glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) from alfalfa (Medicago sativa L.). These exhibit extensive nucleotide and amino acid sequence similarity to the corresponding genes from bacteria, Drosophila and mammals. Transcripts encoding both enzymes are expressed at high levels in roots and nodules. Exposure of alfalfa suspension cells to an elicitor from yeast cell walls results in co-ordinated increases in transcription rates for both genes, followed by increased steady state transcript levels but only slightly increased extractable enzyme activities, at the onset of accumulation of isoflavonoid phytoalexins. Levels of NADPH and NADP remain relatively constant in alfalfa cells following elicitation. The rapid transcriptional activation of 6PGDH and G6PDH does not therefore appear to be a response to altered pyridine nucleotide redox state. These genes appear to respond to early events in elicitor-mediated signalling rather than to subsequent elicitor-induced changes in secondary metabolism. Hydrogen peroxide, a potential signal for elicitation of anti-oxidative genes in biologically stressed plant cells, did not induce 6PGDH or G6PDH transcripts or enzymatic activity.
引用
收藏
页码:885 / 900
页数:16
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