Deciphering Reserve Mobilization, Antioxidant Potential, and Expression Analysis of Starch Synthesis in Sorghum Seedlings under Salt Stress

Salt stress is one of the major constraints affecting plant growth and agricultural productivity worldwide. Sorghum is a valuable food source and a potential model for studying and better understanding the salt stress mechanics in the cereals and obtaining a more comprehensive knowledge of their cellular responses. Herein, we examined the effects of salinity on reserve mobilization, antioxidant potential, and expression analysis of starch synthesis genes. Our findings show that germination percentage is adversely affected by all salinity levels, more remarkably at 120 mM (36% reduction) and 140 mM NaCl (46% reduction) than in the control. Lipid peroxidation increased in salt-susceptible genotypes (PC-5: 2.88 and CSV 44F: 2.93 nmloe/g.FW), but not in tolerant genotypes. SSG 59-3 increased activities of α-amylase, and protease enzymes corroborated decreased starch and protein content, respectively. SSG 59-3 alleviated adverse effects of salinity by suppressing oxidative stress (H2O2) and stimulating enzymatic and non-enzymatic antioxidant activities (SOD, APX, CAT, POD, GR, and GPX), as well as protecting cell membrane integrity (MDA, electrolyte leakage). A significant increase (p ≤ 0.05) was also observed in SSG 59-3 with proline, ascorbic acid, and total carbohydrates. Among inorganic cations and anions, Na+, Cl−, and SO42− increased, whereas K+, Mg2+, and Ca2+ decreased significantly. SSG 59-3 had a less pronounced effect of excess Na+ ions on the gene expression of starch synthesis. Salinity also influenced Na+ ion efflux and maintained a lower cytosolic Na+/K+ ratio via concomitant upregulation of SbNHX-1 and SbVPPase-I ion transporter genes. Thus, we have highlighted that salinity physiologically and biochemically affect sorghum seedling growth. Based on these findings, we highlighted that SSG 59-3 performed better by retaining higher plant water status, antioxidant potential, and upregulation of ion transporter genes and starch synthesis, thereby alleviating stress, which may be augmented as genetic resources to establish sorghum cultivars with improved quality in saline soils.

Vigor and alpha-amylase activity in common bean seeds under salt stress conditions

Seeds with high vigor have greater capacity for hydrolysis and mobilization of stored reserves, which results in the formation of vigorous seedlings, and this behavior is observed under abiotic stress conditions. This study proposes to investigate the relationship of the enzyme alpha-amylase in lots of common-bean seeds with contrasting vigor, when subjected to the absence and presence of salt stress, aiming to identify the relationship of this enzyme with the vigor of the seed lot under these conditions. Seven common-bean cultivars were used. Physiological quality was determined by germination, vigor index and seedling length. The mobilization of reserves was evaluated under absence and presence of salt stress simulated with a NaCl solution with a concentration of 50 mmol L-1. The analyzed variables regarding reserve mobilization were reserve reduction, reserve reduction rate, seedling dry weight, reserve mobilization rate, starch, starch reduction rate and alpha-amylase activity. Results showed that the stress condition negatively affected all the evaluated variables; however, the cultivars classified as having greater vigor showed better physiological performance under stress. Salt stress in common-bean seeds affects seedling performance and reduces alpha-amylase activity during germination, and high-vigor seed lots exhibited higher enzyme activity in the no-stress condition.

Seed Priming With an Animal-derived Protein Hydrolysate Improves Drought Tolerance of Tomato Seeds by Enhancing Reserve Mobilization, Osmotic Adjustment, and Antioxidant Mechanism

Purpose Protein hydrolysates obtained from agro-industrial byproducts have received much attentions due to their positive roles in regulating plant responses to environmental stresses. However, little is known about the roles of animal protein hydrolysates in mediating seed drought tolerance and the underlying mechanism. Here, the effects of seed priming with pig blood protein hydrolysates (PP) on tomato seed germination and seedling growth under drought stress were investigated. Methods Tomato seeds were soaked with different concentrations of PP solutions for 24 h, and then transferred to filter paper moistened with distilled water or 10% PEG-6000 solution in Petri dish. The germination traits, seeding growth, reserve mobilization, osmolytes, and antioxidant system were determined.Results PP priming effectively alleviated the reduction in seed germination traits, resulting in improved tomato seedling growth under drought stress. PP priming enhanced amylase and sucrose synthase activities, soluble sugar, soluble protein, and free amino acid levels, thereby promoting reserve mobilization in seeds. Moreover, PP priming also reduces osmotic toxicity by increasing the accumulation of proline, soluble protein, and soluble sugar. Drought stress substantially enhanced the production of ROS and subsequent increases in MDA and Evans blue uptake, which were significantly alleviated after PP priming by improving the activities of SOD, POD, and CAT, and non-enzymatic antioxidants. Conclusion PP priming is a feasible method for improving tomato seed germination and seedling growth under drought stress by enhancing reserve mobilization, osmolyte accumulation, and antioxidant systems.

Pineapple stem-derived bromelain based priming improves pepper seed protein reserve mobilization and germination

Pepper fruit has a great agronomic, nutritional and commercial value given that it is rich in antioxidant compounds such as carotenes, and vitamins C and E. However, pepper seeds are slow to germinate and emergence is often non-uniform and incomplete. Seed priming and invigoration treatments have been explored for a number of pepper varieties but success has been variable and generally limited. The present report describes the effects of pineapple stem – derived protease (stem bromelain) based priming on pepper seed germination in relation to reserve mobilization (specifically, proteins and aminoacids). Germination capacity in bromelain treated seeds was significantly higher on days 7, 14 and 21 than in unsoaked (control) and deionized water-soaked seeds but comparable across the treatments and the control on day 28. Germination rate was significantly highest in bromelain treated seeds. Light microscopy revealed an abundance of protein bodies in the endosperm of the seeds investigated at before imbibition and when observed over a period of 96 h, these bodies were progressively degraded, with the rate of this degradation being fastest in bromelain treated seeds. Quantitative measurements of protein levels (and free amino content) confirmed this observation. The results motivate the use of bromelain extracts for priming pepper seeds based on their proteolytic activity, since germination is dependent on the availability of crude protein and essential amino acids.