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

This review examines the literature on successful establishment of regenerable cell cultures in the economically important cereal crops. Some of the major trends and strategies for the establishment of in vitro cultures that express totipotency are discussed as well as current approaches. It is apparent that in cereal tissue culture, not all cells express totipotency. Generally the auxin 2,4‐dichlorophenoxyacetic acid (2,4‐D) is critical for the production of regenerable callus; however, the addition of cytokinin can be significant. Meristematic cells from immature tissues are the targets for plant growth regulator action. Some genotypes produce embryogenic cultures, while others are recalcitrant to in vitro manipulation. Regeneration occurs either by somatic embryogenesis or adventitious bud and shoot development with subsequent rooting. In these meristematic tissues, plastids are at the undifferentiated proplastid stage of development. The development of a white, nodulated embryogenic callus in somatic embryogenesis and the formation of green buds during organogenesis suggest divergent modes of plastid differentiation during morphogenesis. Plant growth regulators may be involved with inducing or directing different pathways of plastid differentiation. Genotypic differences in morphogenesis may be due to differences in endogenous hormone levels.