Abstract
Drought stress is a major abiotic factor compromising plant cell physiological and molecular events, consequently limiting crop growth and productivity. Maize (Zea mays L.) is among the most drought-susceptible food crops. Therefore, understanding the mechanisms underlying drought-stress responses remains critical for crop improvement. To decipher the molecular mechanisms underpinning maize drought tolerance, here, we used a comparative morpho-physiological and proteomics analysis approach to monitor the changes in germinating seeds of two incongruent (drought-sensitive wild-type Vp16 and drought-tolerant mutant vp16) lines exposed to polyethylene-glycol-induced drought stress for seven days. Our physiological analysis showed that the tolerant line mutant vp16 exhibited better osmotic stress endurance owing to its improved reactive oxygen species scavenging competency and robust osmotic adjustment as a result of greater cell water retention and enhanced cell membrane stability. Proteomics analysis identified a total of 1200 proteins to be differentially accumulated under drought stress. These identified proteins were mainly involved in carbohydrate and energy metabolism, histone H2A-mediated epigenetic regulation, protein synthesis, signal transduction, redox homeostasis and stress-response processes; with carbon metabolism, pentose phosphate and glutathione metabolism pathways being prominent under stress conditions. Interestingly, significant congruence (R2 = 81.5%) between protein and transcript levels was observed by qRT-PCR validation experiments. Finally, we propose a hypothetical model for maize germinating-seed drought tolerance based on our key findings identified herein. Overall, our study offers insights into the overall mechanisms underpinning drought-stress tolerance and provides essential leads into further functional validation of the identified drought-responsive proteins in maize.
Highlights
IntroductionAs sessile organisms, are constantly subjected to a plethora of abiotic (drought, heat, cold, salinity, metal toxicity, nutrient deficiency, etc.) and biotic (pathogens, herbivores, nematodes, weeds, etc.) stress factors [1]
Crop plants, as sessile organisms, are constantly subjected to a plethora of abiotic and biotic stress factors [1]
20% polyethylene glycol (PEG) treatment significantly (p < 0.01) decreased germination rate (GR), root fresh weight (RFW) and shoot fresh weight (SFW) in the two lines, with the rate of decline being significantly greater in wild-type Vp16 than in mutant vp16 (Figure 1A–C)
Summary
As sessile organisms, are constantly subjected to a plethora of abiotic (drought, heat, cold, salinity, metal toxicity, nutrient deficiency, etc.) and biotic (pathogens, herbivores, nematodes, weeds, etc.) stress factors [1]. All these stress factors impose serious limitations on crop survival, growth and productivity [2,3]. The production and productivity of various crops in such regions will be drastically affected [5] This poses an austere challenge to the food security of the growing world human population, projected to hit above 9 billion people by the year 2050 [7,8]
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