Physiological responses and expression of sugar associated genes in faba bean (Vicia faba L.) exposed to osmotic stress

Abstract

Faba bean (Vicia faba L.) is the major food legume crop in Tunisia. However, its growth and yield is strongly affected by water-limited environments. In this study, osmotic stress exhibited a negative effect on Bachar and Badii cultivar. Nevertheless, the deteriorating effects of osmotic stress were relatively low on studied parameters of Bachar due to its better efficiency to reduce oxidative damage by increasing enzymatic activities such as catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX), accumulation of total chlorophyll (Chlt), soluble sugars and leaf relative water content (RWC). GC-MS analysis determined a total of 11 soluble carbohydrates induced by osmotic stress and differentially accumulated in the both cultivars. Bachar showed elevated levels of mannose, glucose, galactose, ribose, rhamnose and myo-inositol which might help to maintain osmotic adjustment, membranes and proteins protection from the damaging effect of reactive oxygen species. Sugar metabolism related genes (VfNINV3, VfPHS2, VfFRK4, VfHXK1, VfGPI1, VfSTP1.1, VfpGlcT1.1, VfSTP5.1, VfpGlcT1.2, VfSWEET2.1, VfVINV2, VfSUS1, VfPGM1, VfSUT1.1, VfGPT1, VfSPS1, VfSPP1, VfPHS1, VfSUT4.1 and VfTMT1.1) were differentially expressed in both cultivars demonstrating their important roles in sugar accumulation. Most of these genes were upregulated in the leaves of Bachar under moderate and severe stress, which could lead to increase glycolysis and tricarboxylic acid cycle in order to accelerate energy production, necessary to increase osmotic regulation and consequently enhancing the osmotic stress tolerance in that cultivar. Overall, sugars accumulation ability can be used as a useful indicator for the osmotic stress tolerant potential in faba bean breeding programs.

Supplementary information: The online version contains supplementary material available at (10.1007/s12298-021-00935-1).

Keywords: Faba bean; GC–MS; Gene expression; Osmotic stress; Sugar metabolism; qRT-PCR.

Fig. 1

Effects of drought stress on net CO₂ assimilation rate (A), stomatal conductance (B), transpiration rate (C) and intercellular CO₂ concentration (D). Values are means ± SD of three replicates. The same letter indicates no significant difference (p ≤ 0.05)

Fig. 2

Effects of drought stress on RWC (A), total chlorophyll (B), proline (C), H₂O₂ (D), MDA (E), EL (F) and soluble sugars (G). Values are means ± SD of three replicates. The same letter indicates no significant difference (p ≤ 0.05)

Fig. 3

Effects of drought stress on the activities of CAT (A), SOD (B), APX (C) and GPX (D). Values are means ± SD of three replicates. The same letter indicates no significant difference (p ≤ 0.05)

Fig. 4

Heat map representation of the effects of drought stress on the genes expression in the leaf tissues of Bachar and Badii. The heat map was generated based on the log2 fold change (log2(FC)) values (treated/control). Yellow and blue indicate higher and lower expression values, respectively. Intensity of the colors is proportional to the absolute value of log2 of the fold difference in expression

Fig. 5

Proposed model of the sugar regulation in faba bean leaves in response to osmotic stress. Upregulated sugar metabolism related-genes are displayed in black ellipses