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 1 / cation exchangers (CAX) have more calcium (Ca 21 ) 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 Ca 21 hypersensitive yeast phenotypes and also appear to be more specific Ca 21 transporters than sCAX1. We then compared the phenotypes of sCAX1-and CAX4-expressing tomato lines. The sCAX1-expressing tomato lines demonstrate increased vacuolar H 1 /Ca 21 transport, when measured in root tissue, elevated fruit Ca 21 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 Ca 21 levels and shelf life but no deleterious effects on plant growth. These findings suggest that CAX expression may fortify plants with Ca 21

Nutritional impact of elevated calcium transport activity in carrots

“…All of these measures require the application of calciumcontaining solutions to the soil or fruits. Recently, sCAX1 expression has been shown to increase calcium level in tomatoes that increased fruit firmness and prolonged shelf life (10). Aside from the nutritional impact shown here, using sCAX1 expression in a variety of fruits and vegetables also could positively impact plant productivity while decreasing labor costs.…”

“…An Arabidopsis vacuolar calcium antiporter, termed Cation exchanger 1 (CAX1), contains an N-terminal autoinhibitory domain (8,9). Expression of N-terminal truncations of CAX1 (sCAX1) in plants such as potatoes, tomatoes, and carrots increases the calcium content in the edible portion of these foods (7,10,11). Presumably, these sCAX1-expressing plants have heightened sequestration of calcium into the large central plant vacuoles.…”

CAX‐ing a wide net: Cation/H+ transporters in metal remediation and abiotic stress signalling

“…These lines show a number of symptoms similar to Ca 2+ deficiencies, and tomato lines expressing the same deregulated CAX suffer from blossom end rot (Park et al . 2005; De Freitas et al . 2014).…”

Safety Test of Brown Rice Expressing Arabidopsis Calcium Transporter by Feeding Trial in Mice

“…지금까지 칼슘 함량을 증가시키는 CAX 1 유전자에 의해 형질전환체를 획득한 작물은 감자, 토마토, 당 근 등에서 목적유전자의 확인과 발현 여부를 검정하여 후대 검정실험 보고를 하였다 [14][15][16]. 또한 형질전환된 당근을 이 용하여 칼슘함량 분석과 식품학적인 결과가 보고되었다 [7,12].…”