cucumber cotyledon
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2007 ◽  
Vol 7 (1) ◽  
pp. 102-111 ◽  
Author(s):  
Ayumu Sakaguchi ◽  
Toshihiko Miyaji ◽  
Gento Tsuji ◽  
Yasuyuki Kubo

ABSTRACT Kelch repeat proteins are important mediators of fundamental cellular functions and are found in diverse organisms. However, the roles of these proteins in filamentous fungi have not been characterized. We isolated a kelch repeat-encoding gene of Colletotrichum lagenarium ClaKEL2, a Schizosaccharomyces pombe tea1 homologue. Analysis of the clakel2 mutant indicated that ClaKEL2 was required for the establishment of cellular polarity essential for proper morphogenesis of appressoria and that there is a plant signal-specific bypass pathway for appressorium development which circumvents ClaKEL2 function. Clakel2p was localized in the polarized region of growing hyphae and germ tubes, and the localization was disturbed by a microtubule assembly blocker. The clakel2 mutants formed abnormal appressoria, and those appressoria were defective in penetration hypha development into cellulose membranes, an artificial model substrate for fungal infection. Surprisingly, the clakel2 mutants formed normal appressoria on the host plant and retained penetration ability. Normal appressorium formation on the artificial substrate by the clakel2 mutants was restored when cells were incubated in the presence of CaCl2 or exudates from cucumber cotyledon. Furthermore, calcium channel modulators inhibited restoration of normal appressorium formation. These results suggest that there could be a bypass pathway that transduces a plant-derived signal for appressorium development independent of ClaKEL2 and that a calcium signal is involved in this transduction pathway.


HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1081B-1081
Author(s):  
Bruce D. Whitaker ◽  
Gene E. Lester

Increases in phospholipase D (PLD) and lipoxygenase (LOX) activities are thought to play a key role in senescence of mesocarp tissues in muskmelon fruit. We have cloned and characterized two full-length cDNAs, CmPLDα and CmLOX1, encoding PLDα and LOX proteins in honeydew melon (Cucumis melo L. Inodorus Group). Levels of expression of the corresponding genes were determined by semi-quantitative RT-PCR in developing and mature fruit mesocarp tissues (20–60 d after pollination; DAP), and in roots, leaves, and stems from 4-week-old and flowers from 6-week-old plants. The coding regions of CmPLDα1 and CmLOX1 cDNAs are, respectively, 2427 and 2634 nucleotides long, encoding proteins 808 and 877 amino acids in length. CmPLDα1 is most similar to PLDα genes in castor bean, cowpea, strawberry, and tomato (77% nucleotide identity), and is the first cucurbit PLD gene cloned. CmLOX1 has 94% nucleotide identity to a cucumber LOX gene expressed in roots and 80% identity to cucumber cotyledon lipid body LOX. Transcript of CmPLDα1 was much more abundant than that of CmLOX1, but relative levels of transcript in the various organs and tissues were similar for the two genes. Expression was highest in roots, flowers, and fruit mesocarp tissues. CmPLDα1 expression in fruit was high throughout development, although maximum levels occurred at 50 and 55 DAP, respectively, in middle and hypodermal mesocarp. CmLOX1 expression was generally higher in middle than in hypodermal mesocarp with maximum transcript levels at 55 and 50 DAP, respectively. Overall, the patterns of expression of CmPLDα1 and CmLOX1 are consistent with a model in which their encoded enzymes act in tandem to promote or accelerate senescence in fruit mesocarp tissues.


2006 ◽  
Vol 131 (4) ◽  
pp. 544-550 ◽  
Author(s):  
Bruce D. Whitaker ◽  
Gene E. Lester

Increases in phospholipase D [PLD (EC 3.1.4.4)] and lipoxygenase [LOX (EC 1.13.11.12)] activities are thought to play a critical role in senescence of mesocarp tissues in netted and nonnetted muskmelon (Cucumis melo L.) fruits. We have cloned and characterized two full-length cDNAs, CmPLDα1 and CmLOX1, encoding PLDα and LOX proteins in honeydew melon (C. melo Inodorus Group cv. Honey Brew). Relative levels of expression of the corresponding genes were determined by semi-quantitative RT-PCR in developing and mature fruit mesocarp tissues [20-60 d after pollination (DAP)], as well as in roots, leaves, and stems from 4-week-old and flowers from 6- to 7-week-old plants. The coding regions of CmPLDα1 and CmLOX1 cDNAs are, respectively, 2427 and 2634 nucleotides long, encoding proteins 808 and 877 amino acids in length. CmPLDα1 is very similar to PLDα genes from castor bean (Ricinis communis L.), cowpea (Vigna unguiculata L.), strawberry (Fragaria ×ananassa Duch.) and tomato (Lycopersicon esculentum Mill.) (77% nucleotide identity), and is the first PLD gene cloned from a cucurbit species. CmLOX1 has 94% nucleotide identity to a cucumber (Cucumis sativus L.) LOX gene expressed in roots and 80% identity to cucumber cotyledon lipid body LOX. In general, transcript of CmPLDα1 was much more abundant than that of CmLOX1, but relative levels of transcript in the various organs and tissues were similar for the two genes. Expression was highest in roots, flowers, and fruit mesocarp tissues. CmPLDα1 expression in fruit was essentially constitutive throughout development, although maximum levels occurred at 50 and 55 DAP, respectively, in middle and hypodermal mesocarp. CmLOX1 expression was generally higher in middle than in hypodermal mesocarp with maximum transcript levels occurring at 55 and 50 DAP, respectively. Overall, the patterns of expression of CmPLDα1 and CmLOX1 are consistent with a model in which their encoded enzymes act in tandem to promote or accelerate senescence in fruit mesocarp tissues.


2006 ◽  
Vol 28 (1) ◽  
pp. 9-11 ◽  
Author(s):  
Xuejun Yu ◽  
Gaixia Li ◽  
Dan Xu ◽  
Xueliang Dong ◽  
Xiuxiang Qi ◽  
...  

Hydrocolloids ◽  
2000 ◽  
pp. 57-62 ◽  
Author(s):  
Y. Matsumura ◽  
N. Matsuo ◽  
J. Kimata ◽  
K. Matsui ◽  
T. Mori

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