Expression of genes associated with aroma formation derived from the fatty acid pathway during peach fruit ripening.
Changes in characteristic aroma volatiles, levels of fatty acids as aroma precursors, and expression patterns of related genes, including lipoxygenase (LOX), hydroperoxide lyase (HPL), alcohol dehydrogenase (ADH), alcohol acyltransferase (AAT), and fatty acid desaturase (FAD), were studied in peach ( Prunus persica L. Batsch., cv. Yulu) fruit during postharvest ripening at 20 degrees C. Concentrations of n-hexanal, (E)-2-hexenal, (E)-2-hexenol, and (Z)-3-hexenol decreased, whereas the production of (Z)-3-hexenyl acetate, gamma-hexalactone, gamma-octalactone, gamma-decalactone, and delta-decalactone increased with fruit ripening. Lactones showed a clear pattern concomitant with the climacteric rise in ethylene production, with gamma-decalactone being the principal volatile compound at the late ripening stage. Of the LOX family genes, PpLOX2 and PpLOX3 had relatively high transcript levels initially followed by a decline with fruit ripening, while levels of PpLOX1 and PpLOX4 transcripts were upregulated by accumulated ethylene production. Expression of PpHPL1, PpADH1, PpADH2, and PpADH3 showed similar decreasing patterns during ripening. Expression levels of PpAAT1 showed a rapid increase during the first 2 days of postharvest ripening followed by a gradual decrease. Contents of polyunsaturated linoleic and linolenic acids increased, and saturated palmitic acid levels tended to decline as the fruit ripened. The increased levels of unsaturated fatty acids closely paralleled increasing expression of PpFAD1 and PpFAD2. The significance of gene expression changes in relation to aroma volatile production is discussed.
Zhang
Bo
B
Laboratory of Fruit Quality Biology, Huajiachi Campus, Zhejiang University, Hangzhou 310029, China.
Shen
Ji-Yuan
JY
Wei
Wen-Wen
WW
Xi
Wan-Peng
WP
Xu
Chang-Jie
CJ
Ferguson
Ian
I
Chen
Kunsong
K
D000217:Acyltransferases / Q000235:genetics; D000426:Alcohol Dehydrogenase / Q000235:genetics; D000446:Aldehyde-Lyases / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D005030:Ethylenes / Q000096:biosynthesis; D044943:Fatty Acid Desaturases / Q000235:genetics; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D005638:Fruit / Q000737:chemistry / Q000235:genetics* / Q000254:growth & development*; D015870:Gene Expression; D007783:Lactones / Q000032:analysis; D008084:Lipoxygenase / Q000235:genetics; D009812:Odorants / Q000032:analysis*; D027861:Prunus / Q000235:genetics*; D055549:Volatile Organic Compounds / Q000032:analysis / Q000378:metabolism
D005030:Ethylenes; D005227:Fatty Acids; D007783:Lactones; D055549:Volatile Organic Compounds; D003577:Cytochrome P-450 Enzyme System; C036216:ethylene; D000426:Alcohol Dehydrogenase; D008084:Lipoxygenase; D044943:Fatty Acid Desaturases; D000217:Acyltransferases; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase