Moderate Salinity Stress Affects Expression of Main Sugar Metabolism and Transport Genes and Soluble Carbohydrate Content in Ripe Fig Fruits (Ficus carica L. cv. Dottato)

Abstract

Fig trees (Ficus carica L.) are commonly grown in the Mediterranean area, where salinity is an increasing problem in coastal areas. Young, fruiting plants of cv. Dottato were subjected to moderate salt stress (100 mM NaCl added to irrigation water) for 48 days before fruit sampling. To clarify the effect of salinity stress, we investigated changes in the transcription of the main sugar metabolism-related genes involved in the synthesis, accumulation and transport of soluble carbohydrates in ripe fruits by quantitative real-time PCR as well as the content of soluble sugars by quantitative 1H nuclear magnetic resonance spectroscopy. A general increase in the transcript levels of genes involved in the transport of soluble carbohydrates was observed. Alkaline-neutral and Acid Invertases transcripts, related to the synthesis of glucose and fructose, were up-regulated in ripe fruits of NaCl-stressed plants without a change in the content of D-glucose and D-fructose. The increases in sucrose and D-sorbitol contents were likely the result of the up-regulation of the transcription of Sucrose-Synthase- and Sorbitol-Dehydrogenase-encoding genes.

Cations and Phenolic Compounds Concentrations in Fruits of Fig Plants Exposed to Moderate Levels of Salinity

“…In general, transcript levels of genes involved in the transport of soluble sugars in ripe fig fruits were affected by salinity [9]. Alkaline-neutral and acid invertases transcripts were upregulated in salinized plants, as well as the transcription of sucrose-synthase and sorbitol dehydrogenase encoding genes [9]. Other molecular studies showed that the introduction, via Agrobacterium-mediated transformation into the fig cultivar Black Mission, of the gene AgNHX1 (codifying a vacuolar Na/H antiporter in the halophytic species Atriplex gmelini) conferred high tolerance to salinity [14].…”

“…Pigments, non-enzymatic antioxidants, and antioxidative enzymes are all active against oxidative stress [ 6 ] as well as salinity [ 7 ]. Salinity affects the physiology, metabolism, and gene expression of fig trees [ 8 , 9 , 10 ]. In general, saline stress decreases plant water potential, photosynthetic rate, stomatal conductance, growth, and alters biomass partitioning and ion distribution within the plant [ 8 , 11 , 12 , 13 ].…”

“…Fruit characteristics and composition of fig plants grown under saline conditions are poorly defined. A recent article reported that salinity increased sucrose and sorbitol concentrations in fig fruits, but not glucose or fructose [ 9 ]. The expression levels of the main sugar metabolism and transport genes were studied in fig tree under salt stress [ 9 , 22 ].…”

“…A recent article reported that salinity increased sucrose and sorbitol concentrations in fig fruits, but not glucose or fructose [ 9 ]. The expression levels of the main sugar metabolism and transport genes were studied in fig tree under salt stress [ 9 , 22 ]. In general, transcript levels of genes involved in the transport of soluble sugars in ripe fig fruits were affected by salinity [ 9 ].…”

“…The expression levels of the main sugar metabolism and transport genes were studied in fig tree under salt stress [ 9 , 22 ]. In general, transcript levels of genes involved in the transport of soluble sugars in ripe fig fruits were affected by salinity [ 9 ]. Alkaline-neutral and acid invertases transcripts were upregulated in salinized plants, as well as the transcription of sucrose-synthase and sorbitol dehydrogenase encoding genes [ 9 ].…”