Involvement of negative feedback regulation in wound-induced ethylene synthesis in 'Saijo' persimmon

Hormonal control of parthenocarpic fruit set in 'Rojo Brillante' persimmon (Diospyros kaki Thunb.)

In persimmon (Diospyros kaki Thunb.), one to three waves of fruit abscission can occur. The parthenocarpic cv. Rojo Brillante may abscise close to 50% of flowers, which implies a major economic losses. In order to study this process, 700 flowers were labelled, 600 had the lobes of the calyx removed at three stages to promote abscission. Half of them were also treated with gibberellic acid (GA₃; 10 mg l^-1) to counteract the effect, and 100 were used as control. In the second year, GA₃ (25 mg l^-1) was applied to whole trees. Calyx lobe removal (CLR) reduced fruit growth rates and advanced and increased fruitlet abscission, whereas GA₃ counteracted this effect. Furthermore, when GA₃ was applied to the whole tree, fruit set was increased. The time-course of fruit abscission paralleled a decreased in hormonal and carbohydrate contents. Control fruit showed a peak of gibberellin (GA₁ and GA₄) and IAA concentration at anthesis. Hexose concentrations remained almost constant from flower bud to fruit set, whereas that of sucrose diminished with time. A peak in ethylene production occurred at anthesis, which increased when CLR was performed prior to or at anthesis, but not when performed at fruit set, when ethylene was markedly smaller. GA₃ also counteracted it. Accordingly, we suggest that fruit set depends on the induction of gibberellin (GA) and IAA responses in the persimmon, and since there is no shortage of hormones or carbohydrates at anthesis, ethylene production at anthesis seems the most plausible cause of the physiological fruitlet abscission.

Persimmon (Diospyros kaki) fruit: hidden phytochemicals and health claims

Currently, nutrition and health linkages focused on emerging strategy of diet based regimen to combat various physiological threats including cardiovascular disorders, oxidative stress, diabetes mellitus, etc. In this context, consumption of fruits and vegetables is gaining considerable importance as safeguard to maintain human health. Likewise, their phytochemicals and bioactive molecules are also becoming popular as promising demulcent against various ailments. The current review is an effort to sum up information regarding persimmon fruit with special reference to its phytochemistry and associated health claims. Accordingly, the role of its certain bioactive molecules like proanthocyanidin, carotenoids, tannins, flavonoids, anthocyanidin, catechin, etc. is highlighted. Owing to rich phytochemistry, persimmon and its products are considered effective in mitigating oxidative damage induced by reactive oxygen species (ROS). The antioxidant potential is too responsible for anti-malignant and anti-melanogenic perspectives of persimmon functional ingredients. Additionally, they are effectual in soothing lifestyle related disparities e.g. cardiovascular disorders and diabetes mellitus. There are proven facts that pharmacological application of persimmon or its functional ingredients like proanthocyanidin may helps against hyperlipidemia and hyperglycemia. Nevertheless, astringent taste and diospyrobezoars formation are creating lacuna to prop up its vitality. In toto, persimmon and its components hold potential as one of effective modules in diet based therapy; however, integrated research and meta-analysis are still required to enhance meticulousness.

Cross-talk between signaling pathways: the link between plant secondary metabolite production and wounding stress response

Plants subjected to wounding stress produce secondary metabolites. Several of these metabolites prevent chronic diseases and can be used as colorants, flavors, and as antimicrobials. This wound-induced production of plant secondary metabolites is mediated by signaling-molecules such as reactive oxygen species (ROS), ethylene (ET) and jasmonic acid (JA). However, their specific role and interactions that modulate the wound-respond in plants is not fully understood. In the present study, a subtractive cDNA library was generated, to better understand the global response of plants to wounding stress. Carrot (Daucus carota) was used as a model system for this study. A total of 335 unique expressed sequence tags (ESTs) sequences were obtained. ESTs sequences with a putative identity showed involvement in stress-signaling pathways as well as on the primary and secondary metabolism. Inhibitors of ROS biosynthesis, ET action, and JA biosynthesis alone and in combination were applied to wounded-carrots in order to determine, based on relative gene expression data, the regulatory role of ET, JA, and ROS on the wound-response in plants. Our results demonstrate that ROS play a key role as signaling-molecules for the wound-induced activation of the primary and secondary metabolism whereas ET and JA are essential to modulate ROS levels.

Effects of abscisic acid on ethylene biosynthesis and perception in Hibiscus rosa-sinensis L. flower development

The effect of the complex relationship between ethylene and abscisic acid (ABA) on flower development and senescence in Hibiscus rosa-sinensis L. was investigated. Ethylene biosynthetic (HrsACS and HrsACO) and receptor (HrsETR and HrsERS) genes were isolated and their expression evaluated in three different floral tissues (petals, style-stigma plus stamens, and ovaries) of detached buds and open flowers. This was achieved through treatment with 0.1 mM 1-aminocyclopropane-1-carboxylic acid (ACC) solution, 500 nl l(-1) methylcyclopropene (1-MCP), and 0.1 mM ABA solution. Treatment with ACC and 1-MCP confirmed that flower senescence in hibiscus is ethylene dependent, and treatment with exogenous ABA suggested that ABA may play a role in this process. The 1-MCP impeded petal in-rolling and decreased ABA content in detached open flowers after 9 h. This was preceded by an earlier and sequential increase in ABA content in 1-MCP-treated petals and style-stigma plus stamens between 1 h and 6 h. ACC treatment markedly accelerated flower senescence and increased ethylene production after 6 h and 9 h, particularly in style-stigma plus stamens. Ethylene evolution was positively correlated in these floral tissues with the induction of the gene expression of ethylene biosynthetic and receptor genes. Finally, ABA negatively affected the ethylene biosynthetic pathway and tissue sensitivity in all flower tissues. Transcript abundance of HrsACS, HrsACO, HrsETR, and HrsERS was reduced by exogenous ABA treatment. This research underlines the regulatory effect of ABA on the ethylene biosynthetic and perception machinery at a physiological and molecular level when inhibitors or promoters of senescence are exogenously applied.