Morpho-physiological and proteome changes and influence of exogenous application of oil palm wood vinegar (OPWV) on the growth of drought-stressed Pandanus amaryllifolius / Muhammad Asyraf Mohd Amnan

Muhammad Asyraf , Mohd Amnan (2023) Morpho-physiological and proteome changes and influence of exogenous application of oil palm wood vinegar (OPWV) on the growth of drought-stressed Pandanus amaryllifolius / Muhammad Asyraf Mohd Amnan. PhD thesis, Universiti Malaya.

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Abstract

Drought is a significant threat to the agricultural sector, as it can negatively impact plant growth, yield, and survival. However, our understanding of how plants respond to drought stress and recover from it is limited. To address this knowledge gap, further research on the molecular regulation of drought stress signalling in plants is indispensable. Oil palm wood vinegar (OPWV), a waste product from the palm oil industry, potentially mitigates the adverse effects of drought stress on plants. This study hypothesised that drought stress would impact the morphology, physiology, biochemistry, and molecular responses of P. amaryllifolius, and exogenously applying OPWV would alleviate the adverse effects of drought stress. To test this hypothesis, P. amaryllifolius plants were exposed to drought stress for 0, 4, 7, 10 and 14 days before being sampled for the morphological, biochemical and protein response analyses. The results showed that drought stress caused a decreased leaf relative water content (LRWC) and chlorophyll content in P. amaryllifolius. In contrast, the relative electrolyte leakage (REL), proline and malondialdehyde (MDA) contents, and the activities of antioxidant enzymes in the drought-treated and recovered samples were relatively higher than in the well-watered sample. Several abundantly altered proteins of drought-stressed, well-watered, and recovered samples were identified using tandem mass tags (TMT)-based quantitative proteomics. Of the 1415 differentially abundant proteins, 74 were significantly altered. Most proteins differing between them were related to carbon metabolism, photosynthesis, stress response, and antioxidant activity. On the other hand, drought stress enhanced the expression of several drought-responsive genes, such as heat shock protein 70 (HSP70), thaumatin (Thau), enolase (ENO), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-fructofuranosidase (β-Fruc). Applying OPWV to drought-stressed P. amaryllifolius improved plant morphology, such as increased LWRC, stem circumference, root-to-shoot ratio, chlorophyll pigments, and reduced relative electrolyte leakage, leaf yellowing, and leaf folding percentage. OPWV treatment also decreased stress-related indicators, such as hydrogen peroxide, proline, and malondialdehyde, and increased the antioxidants activity, such as superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase. In addition, the relative expression of drought-responsive genes, HSP70 and Thau, was significantly enhanced, while ENO and β-Fruc gene expressions were reduced under drought conditions with OPWV treatment. These findings support the idea that the exogenous application of OPWV enhances drought tolerance in P. amaryllifolius by effecting changes at both morphological and molecular levels. This study provides insights into morpho-biochemical and proteome changes in P. amaryllifolius under drought stress conditions and how OPWV impacts its drought tolerance. These data may provide a potential strategy for minimising growth inhibition due to abiotic stress in agricultural fields.

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