title: Increased calcium levels and prolonged shelf life in tomatoes expressing Arabidopsis H+/Ca2+ transporters.
abstract: Here we demonstrate that fruit from tomato (Lycopersicon esculentum) plants expressing Arabidopsis (Arabidopsis thaliana) H(+)/cation exchangers (CAX) have more calcium (Ca2+) and prolonged shelf life when compared to controls. Previously, using the prototypical CAX1, it has been demonstrated that, in yeast (Saccharomyces cerevisiae) cells, CAX transporters are activated when the N-terminal autoinhibitory region is deleted, to give an N-terminally truncated CAX (sCAX), or altered through specific manipulations. To continue to understand the diversity of CAX function, we used yeast assays to characterize the putative transport properties of CAX4 and N-terminal variants of CAX4. CAX4 variants can suppress the Ca2+ hypersensitive yeast phenotypes and also appear to be more specific Ca2+ transporters than sCAX1. We then compared the phenotypes of sCAX1- and CAX4-expressing tomato lines. The sCAX1-expressing tomato lines demonstrate increased vacuolar H(+)/Ca2+ transport, when measured in root tissue, elevated fruit Ca2+ level, and prolonged shelf life but have severe alterations in plant development and morphology, including increased incidence of blossom-end rot. The CAX4-expressing plants demonstrate more modest increases in Ca2+ levels and shelf life but no deleterious effects on plant growth. These findings suggest that CAX expression may fortify plants with Ca2+ and may serve as an alternative to the application of CaCl2 used to extend the shelf life of numerous agriculturally important commodities. However, judicious regulation of CAX transport is required to assure optimal plant growth.
authors.affiliation: Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX 77845, USA.
authors.forename: Sunghun
authors.initials: S
authors.lastname: Park
authors.forename: Ning Hui
authors.initials: NH
authors.lastname: Cheng
authors.forename: Jon K
authors.initials: JK
authors.lastname: Pittman
authors.forename: Kil Sun
authors.initials: KS
authors.lastname: Yoo
authors.forename: Jungeun
authors.initials: J
authors.lastname: Park
authors.forename: Roberta H
authors.initials: RH
authors.lastname: Smith
authors.forename: Kendal D
authors.initials: KD
authors.lastname: Hirschi
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002241:Carbohydrates / Q000032:analysis; D027682:Cation Transport Proteins / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D005030:Ethylenes / Q000096:biosynthesis; D005638:Fruit / Q000502:physiology; D015870:Gene Expression; D017136:Ion Transport; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010641:Phenotype; D030821:Plants, Genetically Modified; D011522:Protons; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; C460090:CAX4 protein, Arabidopsis; D002135:Calcium-Binding Proteins; D002241:Carbohydrates; D027682:Cation Transport Proteins; D002412:Cations; D005030:Ethylenes; D011522:Protons; C027614:calcium-hydrogen antiporters; C036216:ethylene; D002118:Calcium