Increasing Ascorbic Acid Content and Salinity Tolerance of Cherry Tomato Plants by Suppressed Expression of the Ascorbate Oxidase Gene

Abstract

eg (M.I.A.M.) 2 INRA, UR1052, Génétique et amélioration des fruits et légumes, DomaineAbstract: Ascorbic acid is considered to be one of the most important antioxidants in plants and plays a vital role in the adaptation of plants to unfavorable conditions. In the present study, an ascorbate oxidase gene (Solyc04g054690) was over-expressed in cherry tomato cv. West Virginia 106 lines and compared with previously studied RNAi silenced ascorbate oxidase lines. Two lines with lower ascorbate oxidase activity (AO−15 and AO−42), two lines with elevated activity (AO+14 and AO+16), and the non-transgenic line (WVa106) were grown and irrigated with 75 mM and 150 mM NaCl in 2015 and 2016. Growth, yield, and chemical composition of the lines under salinity stress were evaluated. Lines with lower ascorbate oxidase activity resulted in higher plant growth parameters (plant height, leaf number, flower, and cluster number in 2015 and stem diameter and flower number in 2016), and improved fruit quality (firmness in 2016 and soluble solid content in 2015) and total yield per plant under salinity stress over both years. In addition, we show that ascorbic acid, lycopene, and carotene contents of fruits were higher in lines with lower ascorbate oxidase activity compared to lines with elevated activity and the non-transgenic line under conditions of moderate and high salinity in both years. cancer, including prostate, colon, and breast cancers [4]. Tomato fruits have a considerable amount of ascorbic acid (AA) (or vitamin C), which ranged from 84 to 590 mg/kg [5,6]. In addition, nearly one hundred grams of tomato can provide 40% of the recommended amount of AA for an adult's daily nutritional requirements. AA is considered to be one of the most abundant antioxidants found in the plant, including the apoplast [7]. There are several factors affecting AA levels in plants, such as the genetic background, environmental conditions, seasons, and abiotic stress, such as drought and salinity [8]. Previous work showed that application of exogenous AA leads to increased salt tolerance in tomato [2]. It was reported that breeders should be developing horticultural crops with high ascorbic acid content [9]. In plants, ascorbic acid is oxidized by ascorbate oxidase (AO) (an apoplastic enzyme) to mono-dehydroascorbate (MDHA) [10].The activity of AO plays a role in regulating the redox state (the ratio of reduced to total AA) of the apoplast [11]. A positive relationship has been found between the level of AO activity and abiotic stress tolerance. AO is also highly expressed in fruits and roots of tomato [12].Under-expression of the AO enzyme often leads to increased abiotic stress tolerance, such as to drought in tomato [11] and to salt in Arabidopsis and tobacco [13]. By contrast, the over-expression of AO leads to increased sensitivity to stress [7].In a previous study [11], West Virginia 106 cherry tomato cotyledons were transformed to create two RNAi silenced lines (AO−15 and AO−42) with lower AO activity. In this work, the authors found that t...

Response of seven African eggplant (Solanum macrocarpon L.) cultivars produced in Benin to salinity stress at seedling stage

“…The presence of NaCl salt in the plant growing medium inhibited the growth of both aerial part and roots of the young plants of all the 7 cultivars. The reduction of plant growth by salt stress is a current phenomenon as reported in several vegetables species including tossa jute (Ghosh et al, 2013;Ben Yakoub et al, 2019), amaranth amaranth (Omami et al, 2005;; pepper (Sikha et al, 2013;R'him et al, 2013): tomato (Abir et al, 2006;Albacete et al, 2008;Ould Mohamdi et al, 2011;Abdelgawad et al, 2019 ; Our results revealed variability among the response of the 7 cultivars to salt stress according to the growth parameter.…”

Vitamin C in Plants: From Functions to Biofortification

“…The enhancement of vitamin C in silenced MDHAR lines could be due to a decrease in degradation [44]. In cherry tomato, the suppression of AOX was also found to increase vitamin C, lycopene, and carotene contents of the fruits and to confer tolerance to salt stress [222].…”

Accumulation of Ascorbic Acid in Tomato Cell Culture: Influence of the Genotype, Source Explant and Time of In Vitro Cultivation

“…An ascorbate peroxidase was overexpressed in all genotypes, although its activation may be multifactorial. For fieldgrown tomato, the relation between AO and AsA content in mature fruits is complex, because transgenic lines with either higher or lower AO activity had higher AsA amount than control lines [50]. In pepper, in addition of a positive correlation between AO activity and AsA level [51], the role of the AO gene has been connected with the regulation of cell division and growth in expanding tissues [52].…”