Mechanisms Involved in Calcium Deficiency Development in Tomato Fruit in Response to Gibberellins

Abstract

Although gibberellins (GAs) have been shown to induce development of the physiological disorder blossom-end rot (BER) in tomato fruit (Solanum lycopersicum), the mechanisms involved remain largely unexplored. BER is believed to result from calcium (Ca) deficiency, but the relationship between Ca content and BER incidence is not strong. Our objectives were to better understand how GAs and a GA biosynthesis inhibitor affect BER development in tomato fruit. Tomato plants of two BER-susceptible cultivars, 'Ace 55 (Vf)' and 'AB2,' were grown in a greenhouse environment and subjected to Ca-deficiency conditions. Plants were treated weekly during fruit growth and development with 300 mg L -1 GA 4?7 , 300 mg L -1 prohexadione-calcium (Apogee Ò , a GA biosynthesis inhibitor), or water beginning 1 day after flower pollination. GA 4?7 treatment induced an increase in BER incidence in both cultivars up to 100%, whereas 'Ace 55 (Vf)' and 'AB2' plants treated with Apogee did not show BER incidence. The number of functional xylem vessels was higher in the placental and pericarp tissue of tomato fruit treated with Apogee at the early stages of fruit growth. Treatment with Apogee also increased fruit pericarp Ca concentration. GA 4?7 treatment enhanced the expression of the putative CAX and Ca-ATPase genes, that code for proteins involved in Ca movement into storage organelles. The lowest watersoluble apoplastic Ca concentration and the highest membrane leakage values were observed in the pericarp of GA 4?7 -treated fruit. These results suggest that GAs consistently reduced fruit Ca uptake and water-soluble apoplastic Ca concentration, leading to leakier plasma membranes and an increase in BER development in fruit tissue of both tomato cultivars.

Pepper Crop under Climate Change: Grafting as an Environmental Friendly Strategy

“…Low Ca 2+ in the nutrient medium has been indicated to result in very extensive root systems, which suggests great GA activity. Accordingly, a low Ca 2+ supply might have caused the high BER incidence more indirectly through enhanced GA activity [88]. ABA, as an antagonist to GAs, is known for reducing plant susceptibility to stress; e.g., by promoting Ca 2+ transport to fruits.…”

“…ROS are known to trigger cell death, which is characterized by the progressive loss of membrane integrity to result in cytoplasm swelling, and also in the release of cellular constituents [98], including loss of Ca 2+ ions, which may explain the lower Ca 2+ concentrations found mainly in the apoplast [88]. A certain amount of stress, caused by either a single or an interaction of several environmental factors, like high relative humidity, pathogenic stem diseases, and dry or saline soils, may have a negative effect on calcium uptake [99], which does not always end in a corresponding degree of BER [90].…”

Screening Pepper Genotypes to Obtain Tolerant Rootstocks to Salt and Water Stress: Physiological and Agronomical Responses of the Grafted Plants

“…Symptoms are associated with the membrane leakage of cell solutes, cell plasmolysis, and membrane breakdown (de Freitas et al, 2012;Ho and White, 2005;Saure, 2001). Subsequently, the fruit surface exhibits water-soaked symptoms, and the tissue at the distal portion of the fruit becomes discoloured and necrotic.…”

“…Low Ca 2+ in the nutrient medium has been reported to result in the most extensive root systems, and indicates high GA activity. In this case, a low supply of Ca 2+ may have caused the high BER incidence more indirectly via increased GA activity (de Freitas et al, 2012).…”

Physiological and morphological mechanisms regulating blossom-end rot in tomato fruits

“…The use of gibberellin was shown to promote plant growth (Serrani et al, 2007), however it was noted that there was an increase in the incidence of BER (De Freitas et al, 2012b). The mechanism by which gibberellins increase the incidence of BER are linked to accelerated growth and absence of Ca…”