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Milton E. Tignor, Frederick S. Davies, Wayne B. Sherman, and John M. Davis

Poncirus trifoliata (L.) Raf. seeds were germinated in perlite under intermittent mist at about 25 °C and natural daylight in a greenhouse. Two-week-old seedlings were then transferred into a growth chamber at 25 °C and 16-hour daylength for 1 week. Tissue samples were collected at 0, 6, 24, 168, and 504 hours after temperature equilibration at 10 °C. Freezing tolerance at –6.7 °C, as determined by electrolyte leakage, and stem (leaves attached) water potential (ψx), measured using a pressure chamber, was recorded for a subset of seedlings for each time interval. Red coloration (apparently anthocyanin) developed at the petiole leaflet junction and buds after 48 hours at 10 °C and gradually occurred throughout the leaves during further exposure. Complementary DNA clones for phenylalanine ammonia lyase (PAL), 4-coumarate: coA ligase (4CL), and chalcone synthase (CHS) were used to probe RNA isolated from the leaves. No increase in steady-state messenger RNA level was detected. Increases in freeze hardiness occurred within 6 hours in the leaves, and continued for up to 1 week. Water potential initially decreased from –0.6 to –2.0 MPa after 6 hours, then returned to –0.6 MPa after 1 week. Thus, Poncirus trifoliata seedlings freeze-acclimate significantly after only 6 hours at 10 °C.

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Milton E. Tignor, John M. Davis, Frederick S. Davies, and Wayne B. Sherman

Poncirus trifoliata is a comparatively hardy, cross compatible, and graft compliant relative of Citrus. The citrus industry in Florida has suffered immense economic losses due to freezes. Although much research has been done in citrus freeze hardiness, little work has been on the early induction of freeze tolerance by low temperature. Poncirus trifoliata `Rubidoux' seedlings were germinated in perlite under intermittent mist at about 25°C and natural daylight conditions in a greenhouse and grown 2 weeks. See dlings were then transferred into a growth chamber at 25°C and 16 hour daylength for 1 week. Temperature was lowered to 10°C and tissue samples were collected at 0, 6, 24, and 168 hours. Freezing tolerance, at –6.7°C as determined by electrolyte leakage, and stem (leaves attached) water potential, measured using a pressure bomb, were also recorded for a subset of seedlings for the above intervals. After exposure to low temperature for 48 hours a red coloration became visible at the petiole leaflet junction an d at the buds, with subsequent exposure to low temperature the coloration spread to the leaves. Clones for phenylalanine ammonia lyase (PAL), 4-coumarate:CoA ligase (4CL), and chlorophyll ab binding protein (CAB), and chalcone synthase (CHS) were used to probe RNA isolated from P. trifoliata. PAL and 4CL transcripts increased in response to the low temperature. Significant increases in freeze hardiness occurred within 6 hours in the leaves, and increases continued for up to one week. Water potential increased from –0.6 to –2.0 MPa after 6 hours, then returned to –0.6 MPa after 1 week. These data indicate that increases in freezing tolerance and changes in water potential and gene expression can be detected shortly after low temperature treatments are imposed on P. trifoliata seedlings.

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Ayako Ikegami, Keizo Yonemori, Akira Kitajima, Akihiko Sato, and Masahiko Yamada

Expression patterns of the genes involved in condensed tannin (CT) biosynthesis during fruit development was investigated in a Chinese pollination-constant, nonastringent (PCNA) persimmon (Diospyros kaki Thunb.) `Luo Tian Tian Shi'. The transcript levels of phenylalanine ammonia-lyase (PAL) and dihydroflavonol reductase (DFR) in `Luo Tian Tian Shi' were detected at high levels throughout the fruit growth. Chalcone synthase (CHS) and flavonol 3-hydroxylase (F3H) also continued to be transcribed during fruit growth, although their levels decreased earlier than PAL and DFR. In contrast, expression levels of these genes declined into undetectable levels at an early stage of fruit development in Japanese PCNA persimmon. In addition, anthocyanidin reductase (ANR), which encodes a key enzyme of the proanthocyanidin biosynthesis, was transcribed at high levels in `Luo Tian Tian Shi' during fruit growth, but not in Japanese PCNA persimmon. By contrast, the expression of D. kaki serine carboxypeptidase-like protein 1 (DkSCPL1) that was obtained from suppression subtractive hybridization (SSH) analysis between artificially astringency-removed fruit and astringent fruit in a different experiment, declined earlier than the other flavonoid biosynthesis genes in `Luo Tian Tian Shi', coincident with the termination of the tannin cell development. In the F1 progeny of the cross between `Luo Tian Tian Shi' and Japanese PCNA `Taishu', similar expression patterns were obtained among segregated PCNA and astringent offspring. These results indicate that Chinese PCNA is different from Japanese PCNA in expression of the genes involved in CT biosynthesis. In conclusion, we clarified that expression of the genes (PAL to ANR, but not SCPL) involved in flavonoid biosynthesis was continuous in the Chinese PCNA cultivar, despite the termination of tannin cell development.

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Robert J. Griesbach, Ronald M. Beck, John Hammond, and John R. Stommel

been extensively studied. There is an absence of chalcone synthase enzyme (CHS) activity in the white tissue compared with the colored tissue ( Mol et al., 1983 ). A more complete analysis of structural gene expression in the Star mutant demonstrated

Open access

Kai-Xiang Li, Kai Liu, Yingying Chen, Xiaolu Huang, Wenhui Liang, Baocai Li, Yingbai Shen, and Haiying Liang

and tea plant ( Camellia sinensis ). In A. thaliana , key enzyme genes involved in flavonoid biosynthesis, including chalcone synthase ( CHS ), chalcone flavanone isomerase ( CHI ), flavanone 3-hydroxylase ( F3H ), and flavonol synthase ( FLS ), are

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John R. Stommel, Gordon J. Lightbourn, Brenda S. Winkel, and Robert J. Griesbach

by inhibiting miRNA or siRNA formation responsible for absence of chalcone synthase ( Koseki et al., 2005 ). Further studies are planned to examine anthocyanin biosynthetic and regulatory miRNA genes in C. annuum . Literature Cited

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Xiaohong Wang, Bishun Ye, Xiangpeng Kang, Ting Zhou, and Tongfei Lai

-carotene desaturase; CRTISO, carotenoid isomerase; β-CYC, β-cyclase; β-LCY, lycopene β-cyclase; ε-LCY, lycopene ε-cyclase; β-CRTR, β-carotene hydroxylase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3-hydroxylase; F3′H, flavonoid 3′-hydroxylase

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Ji Tian, Zhen-yun Han, Li-ru Zhang, Ting-Ting Song, Jie Zhang, Jin-Yan Li, and Yuncong Yao

indicated as follows: PAL, phenylalanine ammonium lyase-1; C4H, cinnamate-4-hydroxylase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3-hydroxylase; DFR, dihydroflavonol 4-reductase; ANS, anthocyanidin synthase; GT, uridine diphosphate

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Elysia K. Krieger, Edwards Allen, Larry A. Gilbertson, James K. Roberts, William Hiatt, and Rick A. Sanders

297 2053 2056 Metzlaff, M. O'Dell, M. Cluster, P.D. Flavell, R.B. 1997 RNA-mediated RNA degradation and chalcone synthase A silencing in petunia Cell 88 845 854 Redenbaugh, K

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Mary Woodhead, Ailsa Weir, Kay Smith, Susan McCallum, Katrin MacKenzie, and Julie Graham

contains a PKS1 gene ( Kassim et al., 2009 ). Like the PKS1 gene, Ri PKS5 is also a chalcone synthase ( Zheng and Hrazdina, 2008 ), and the proximity of these genes on this linkage group may indicate a cluster of PKS, and perhaps other genes, involved in