Grafting Watermelon Onto Pumpkin Increases Chilling Tolerance by Up Regulating Arginine Decarboxylase to Increase Putrescine Biosynthesis

Abstract

Low temperature is a major environmental factor that severely impairs plant growth and productivity. Watermelon (Citrullus lanatus) is a chilling-sensitive crop. Grafting of watermelon onto pumpkin rootstock is an effective technique to increase the chilling tolerance of watermelon when exposure to short-time chilling stress. However, the mechanism by which pumpkin rootstock increases chilling tolerance remains poorly understood. Under 10°C/5°C (day/night) chilling stress treatment, pumpkin-grafted watermelon seedlings showed higher chilling tolerance than self-grafted watermelon plants with significantly reduced lipid peroxidation and chilling injury (CI) index. Physiological analysis revealed that pumpkin rootstock grafting led to the notable accumulation of putrescine in watermelon seedlings under chilling conditions. Pre-treat foliar with 1 mM D-arginine (inhibitor of arginine decarboxylase, ADC) increased the electrolyte leakage (EL) of pumpkin-grafted watermelon leaves under chilling stress. This result can be ascribed to the decrease in transcript levels of ADC, ornithine decarboxylase, spermidine synthase, and polyamine oxidase genes involved in the synthesis and metabolism of polyamines. Transcriptome analysis showed that pumpkin rootstock improved chilling tolerance in watermelon seedlings by regulating differential gene expression under chilling stress. Pumpkin-grafted seedling reduced the number and expression level of differential genes in watermelon scion under chilling stress. It specifically increased the up-regulated expression of ADC (Cla97C11G210580), a key gene in the polyamine metabolism pathway, and ultimately promoted the accumulation of putrescine. In conclusion, pumpkin rootstock grafting increased the chilling tolerance of watermelon through transcription adjustments, up regulating the expression level of ADC, and promoting the synthesis of putrescine, which ultimately improved the chilling tolerance of pumpkin-grafted watermelon plants.

Complex Interplay of Metabolic Pathways in Grafting of Ziziphus Species: Transcriptomic Insights into Regulatory Networks of Carbohydrates and Secondary Metabolite Biosynthesis

“…Grafting can alter secondary metabolite accumulation, impacting scion growth, quality, and stress tolerance [18,[56][57][58][59][60]. Strong rootstocks were used to enhance the resistance of scions, using rootstocks to enhance the disease resistance of potatoes, using pumpkin as rootstock to enhance the cold resistance of cucumber and watermelon scions, by upregulating the key genes in the carbon fixation, photosynthesis, and polyamine metabolism pathway [61,62]. By overexpressing the key gene, MdFRK2, of sugar metabolism in the apple rootstock, drought resistance was improved [63].…”

WRKY41/WRKY46-miR396b-5p-TPR module mediates abscisic acid-induced cold tolerance of grafted cucumber seedlings

“…Grafting is one of the most commonly used techniques in vegetable crop production, which can improve stress tolerance, yield, and quality of vegetables ( Shi et al, 2019 ; Wei et al, 2019 ; Darre et al, 2022 ). In recent years, many studies have shown that the cold tolerance of vegetable crops can be improved by grafting onto tolerant rootstock by maintaining higher photosynthesis, enhancing antioxidant activity to scavenge excess reactive oxygen species (ROS) ( Xu et al, 2016 ; Lu J. et al, 2022 ; Luan et al, 2022 ), but information regarding the molecular mechanism of grafting in increasing cold tolerance remains largely unknown. In this study, we found that cucumber seedlings grafted onto figleaf gourd significantly increased the tolerance to cold stress through promoting the accumulation of ABA to induce the expression of WRKY41 and WRKY46 , which further activated the expression of miR396b-5b to target cleavage of TPR .…”

Advances in understanding cold tolerance in grapevine

“…Grafting is an important agronomic technology to improve the quality traits and/or tolerance of scions to environmental stresses. Enhanced cold tolerance of grafted seedlings has been accomplished recently in watermelon ( Citrullus lanatus ) and cucumber ( Cucumis sativus ), respectively ( Lu et al 2022 ; Sun et al 2022 ). Actually, grafting with grapevine rootstocks could promote expression of numerous TFs and accumulation of stilbene, flavonol, and ABA in scions ( Chitarra et al 2017 ; Zhang et al 2022a ).…”