Abstract
Intensive investigations have been conducted on the effect of sole drought or salinity stress on the growth of plants. However, there is relatively little knowledge on how plants, particularly woody species, respond to a combination of these two stresses although these stresses can simultaneously occur in the field. In this study, mulberry, an economically important resource for traditional medicine, and the sole food of domesticated silkworms was subjected to a combination of salt and drought stress and analyzed by physiological methods and TMT-based proteomics. Stressed mulberry exhibited significant alteration in physiological parameters, including root/shoot ratio, chlorophyll fluorescence, total carbon, and ion reallocation. A total of 577 and 270 differentially expressed proteins (DEPs) were identified from the stressed leaves and roots, respectively. Through KEGG analysis, these DEPs were assigned to multiple pathways, including carbon metabolism, photosynthesis, redox, secondary metabolism, and hormone metabolism. Among these pathways, the sucrose related metabolic pathway was distinctly enriched in both stressed leaves and roots, indicating an important contribution in mulberry under stress condition. The results provide a comprehensive understanding of the adaptive mechanism of mulberry in response to salt and drought stress, which will facilitate further studies on innovations in terms of crop performance.
Highlights
Soil salinity and water deficit are the two most common abiotic stresses that constrain plant growth and productivity [1]
At the end of the treatment, in comparison to mulberry trees grown under normal conditions, trees grown under salt and drought stress conditions showed symptoms, such as dwarf and petiole droop (Figure 1)
The root/shoot (R/S) biomass ratio increased from 0.12 under normal conditions to 0.26 under stressed conditions in mulberry (Table 1), which implied that plant resource (e.g., C and N) partitioning may have been prioritized to roots over shoots under salt-drought stress conditions, as occurred in previous reports on mastic trees [26] and Sorhum bicolor [27]
Summary
Soil salinity and water deficit are the two most common abiotic stresses that constrain plant growth and productivity [1]. Salt inhibits many enzymatic processes, including photosynthesis, due to the imbalance of cellular K+/Na+ [2]. Dehydration reduces cell water availability, disrupts normal cellular activities, and compromises photosynthesis [3]. Intensive investigations of regulatory mechanisms under salt or drought stress have been conducted on many plants, including Arabidopsis [4], rice [5], wheat [6], Malus [7], maize [8] and cotton [9]. Relatively little has been reported on intrinsic responses to a combination of two or more stressors, this commonly occurs in the field. Plants confronted with a combination of stressors often produce unpredictable changes, and the involved signaling pathways cannot be directly extrapolated from the study of these stresses individually [10,11,12,13]
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