Abstract
Drought stress is one of the potent abiotic stress limiting cassava (Manihot esculenta) yield globally, but studies addressing both physiological and proteomic responses that how cassava crops can adjust their growth and metabolism under drought conditions are lacking. Combining leaf physiological and proteomic characteristics strongly allied with drought tolerance should results in enhanced drought tolerance in cassava crop. Therefore, the aims of this study were to explore the plant physiological and proteomic mechanisms involved in drought adaptation in cassava. Xinxuan 048 (XX048) was exposed to well-watered control (CK, relative soil water content (RSWC) as 80 ± 5%), mild drought stress (LD, RSWC as 65 ± 5%), moderate drought stress (MD, RSWC as 50 ± 5%) and severe drought stress (SD, RSWC as 35 ± 5%) from 30 days after planting. Under drought stress conditions, cassava plant showed a substantial decline in plant height, stem diameter, leaf number, leaf water content, the ratio of free water content to bound water content of leaf (FW/BW), net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) compared with well watered plants. However, compared with control, leaf water content, SPAD value, cell membrane permeability, malondialdehyde (MDA), soluble sugar, protein proline content SOD and CAT activity were at peak under drought stress. The proteomic analysis revealed that among 3 339 identified proteins, drought stress increased and decreased abundance of 262 and 296 proteins, respectively, compared with control condition. These proteins were involved in carbohydrate energy metabolism, protein homeostasis, transcription, cell structure, cell membrane transport, signal transduction, stress and defense responses. These data not only provides a comprehensive dataset on overall proteomic changes in cassava leaves under drought stress, but also highlights the mechanisms by which euphorbiaceae plants can adapt to drought conditions.
Highlights
Drought was considered as one of the most important abiotic stresses that intimidate the plants’ survival including crops[1]
The morphological and physiological responses of the drought-tolerant cultivar XX048, against light (LD), moderate (MD) and severe (SD) drought stress levels were investigated with 6-month old plants exposed to different drought treatments for five months within the greenhouse
Variations of the photosynthesis parameters of cassava leaves under drought treatment were investigated and net photosynthesis (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and leaf transpiration rate (Tr) were significantly influenced with the increased drought intensity (Fig. 1D–G)
Summary
Drought was considered as one of the most important abiotic stresses that intimidate the plants’ survival including crops[1]. Cassava shows strong tolerance to marginal environments, its production is still constrained by drought. Genetic improvement for drought adaptation in cassava is being enhanced by characterizing the crucial genes of the plant’s responding factors to abiotic stress, i.e. ethylene response factor family genes[7], aquaporin family genes[8], TCP transcription factors[9], the mitogen-activated protein kinase kinase kinases gene family[10], calcium sensors[11], the KT/HAK/KUP family[12], the late embryogenesis abundant protein family[13]. Drought stress affects the growth, the morphological structure, photosynthetic characteristics, physiological and biochemical characteristics of plants[14,15,16,17]. Plants adopt numerous adaptive approaches in response to drought stress, comprising escape, evasion and tolerance mechanisms, and among these strategies, one of the best is antioxidant enzymes production. When membrane integrity was disrupted by stress, vital solutes will emerge from the organelles[26], resulting in electrolyte leakage (EL)
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