Chitosan regulates metabolic balance, polyamine accumulation, and Na+ transport contributing to salt tolerance in creeping bentgrass

Abstract

Background Chitosan (CTS), a natural polysaccharide, exhibits multiple functions of stress adaptation regulation in plants. However, effects and mechanism of CTS on alleviating salt stress damage are still not fully understood. Objectives of this study were to investigate the function of CTS on improving salt tolerance associated with metabolic balance, polyamine (PAs) accumulation, and Na+ transport in creeping bentgrass (Agrostis stolonifera). Results CTS pretreatment significantly alleviated declines in relative water content, photosynthesis, photochemical efficiency, and water use efficiency in leaves under salt stress. Exogenous CTS increased endogenous PAs accumulation, antioxidant enzyme (SOD, POD, and CAT) activities, and sucrose accumulation and metabolism through the activation of sucrose synthase and pyruvate kinase activities, and inhibition of invertase activity. The CTS also improved total amino acids, glutamic acid, and γ-aminobutyric acid (GABA) accumulation. In addition, CTS-pretreated plants exhibited significantly higher Na+ content in roots and lower Na+ accumulation in leaves then untreated plants in response to salt stress. However, CTS had no significant effects on K+/Na+ ratio. Importantly, CTS enhanced salt overly sensitive (SOS) pathways and also up-regulated the expression of AsHKT1 and genes (AsNHX4, AsNHX5, and AsNHX6) encoding Na+/H+ exchangers under salt stress. Conclusions The application of CTS increased antioxidant enzyme activities, thereby reducing oxidative damage to roots and leaves. CTS-induced increases in sucrose and GABA accumulation and metabolism played important roles in osmotic adjustment and energy metabolism during salt stress. The CTS also enhanced SOS pathway associated with Na+ excretion from cytosol into rhizosphere, increased AsHKT1 expression inhibiting Na+ transport to the photosynthetic tissues, and also up-regulated the expression of AsNHX4, AsNHX5, and AsNHX6 promoting the capacity of Na+ compartmentalization in roots and leaves under salt stress. In addition, CTS-induced PAs accumulation could be an important regulatory mechanism contributing to enhanced salt tolerance. These findings reveal new functions of CTS on regulating Na+ transport, enhancing sugars and amino acids metabolism for osmotic adjustment and energy supply, and increasing PAs accumulation when creeping bentgrass responds to salt stress.

Foliar application of chitosan improves plant biomass, physiological and biochemical attributes of rose (Gruss-an-Teplitz)

“…Higher chlorophyll pigments in the present study showed increased photosynthetic activity that significantly increased plant biomass of Gruss-an-Taplitz. Similar correlation of increased chlorophyll with improved growth in bent grass was recorded by Geng et al (2020). Ct provides extra amino groups for chlorophyll synthesis and protects the chlorophyll a from degradation (Wolf, 1956;Muley et al, 2019).…”

Exogenous Application of Chitosan Alleviate Salinity Stress in Lettuce (Lactuca sativa L.)

“…Our study indicates that salinity decreased leaf RWC substantially; however, the exogenous application of CTS positively affected the leaf RWC of the lettuce exposed to saline conditions (Table 2). Geng et al [24] also found that exogenous CTS application significantly increased the leaf RWC and water use efficiency in creeping bentgrass under salt stress, which contributes to maintaining a better water status in plants exposed to salinity stress. Thus, the results obtained from the current study were possibly due to the regulation of the balance between the water supply and leaf transpiration in the lettuce of the NaCl + CTS group.…”

“…A previous study has shown that polysaccharides enhanced salt tolerance in wheat by maintaining a high K + /Na + ratio through regulation of several Na + /K + transporter genes, coordinating the efflux and compartmentation of Na + [58]. The study of Geng et al [24] found that CTS enhanced salt overly sensitive pathways and upregulated the expression of AsHKT1 and genes encoding Na + /H + exchangers under saline conditions, thus inhibiting Na + transport to the photosynthetic tissues. In the present study, although the lower Na + content in leaves was observed in the NaCl + CTS group at harvest time, the Na + levels in shoot and root were not evaluated in a time-response manner, and the gene expressions related to Na + transport still have to be analyzed.…”

“…CTS is a natural, low-toxicity, biodegradable, environmentally friendly, renewable, and inexpensive resource and has many applications in the agriculture sector [19]. Since the discovery of CTS by Rouget in 1859 [20], several studies have proven its role in enhancing plant growth and increasing plants' abiotic stress tolerance [21], including rice [19], maize [22], safflower and sunflower [23], and creeping bentgrass [24]. The beneficial role of CTS in stress mitigation is broadly attributable to the alleviation of oxidative stress [25] and the increase in water use efficiency [26], mineral nutrient uptake [27], chlorophyll (Chl) content, and photosynthesis [28] caused by CTS.…”

Chitosan (CTS) Alleviates Heat-Induced Leaf Senescence in Creeping Bentgrass by Regulating Chlorophyll Metabolism, Antioxidant Defense, and the Heat Shock Pathway

“…Previous studies found that cowpea ( Vigna unguiculata ) leaves sprayed with 250 mg/L of CTS promoted Chl content and carbohydrate accumulation under drought stress [ 25 ]. Salt- or drought-induced water loss in leaves could be effectively alleviated by the exogenous application of CTS, which is associated with the enhancement of sugar accumulation and metabolism for improved osmotic adjustment (OA) in leaves of white clover and creeping bentgrass [ 17 , 18 , 26 ]. The maintenance of better photosynthetic capacity could be one of the most important factors for CTS-regulated sugar production and metabolism in creeping bentgrass under salt and drought stress [ 18 , 26 ].…”