title: Application of γ-aminobutyric acid demonstrates a protective role of polyamine and GABA metabolism in muskmelon seedlings under Ca(NO3)2 stress.
abstract: The effects of exogenous γ-aminobutyric acid (GABA) application on growth, polyamine and endogenous GABA metabolism in muskmelon leaves and roots were measured. Plants were treated under control or 80 mM Ca(NO3)2 stress conditions with or without foliar spraying 50 mM GABA. Ca(NO3)2 stress significantly suppressed seedling growth and GABA transaminase activity, and enhanced glutamate decarboxylase (GAD) activity and endogenous GABA levels. Polyamine (PA) biosynthesis and degradation capacity increased in parallel with increasing GAD activity. Exogenous GABA application effectively alleviated the growth inhibition caused by Ca(NO3)2 stress, and significantly enhanced the activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC), polyamine oxidase (PAO), and diamine oxidase (DAO). Exogenous GABA also significantly reduced the accumulation of free putrescine (Put) and increased the levels of free spermidine (Spd) and spermine (Spm) in leaves, which improved the capacity for polyamine biosynthesis. Application of exogenous GABA under Ca(NO3)2 stress enables the plants to maintain a higher ratio of free Spd and free Spm with respect to free Put. Our data suggest that exogenous GABA has an important role in improving muskmelon seedling tolerance to Ca(NO3)2 stress by improving biosynthesis of PAs and GABA, and by preventing PA degradation. There is a potential positive feedback mechanism that results from higher endogenous GABA content and the combined effects of Ca(NO3)2 stress and exogenous GABA, which coordinately alleviate Ca(NO3)2 stress injury by enhancing PA biosynthesis and converting free Put to an insoluble bound PA form, and reduce PA degradation in muskmelon seedlings.
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China. Electronic address: hxh1977@163.com.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Hu
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China.
authors.forename: Zhiran
authors.initials: Z
authors.lastname: Xu
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China.
authors.forename: Weinan
authors.initials: W
authors.lastname: Xu
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China.
authors.forename: Jianming
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhao
authors.affiliation: College of Horticulture, Northwest Agricultural and Forestry University, Yangling 712100, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest Agricultural & Forestry University, Yangling 712100, China; Key Laboratory of Protected Horticultural Engineering in Northwest, Ministry of Agriculture, Shaanxi, Yangling 712100, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D000612:4-Aminobutyrate Transaminase; D000222:Adaptation, Physiological; D012437:Adenosylmethionine Decarboxylase / Q000378:metabolism; D006631:Amine Oxidase (Copper-Containing) / Q000378:metabolism; D017610:Calcium Compounds / Q000378:metabolism*; D028462:Cucumis / Q000187:drug effects* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009955:Ornithine Decarboxylase / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D011073:Polyamines / Q000378:metabolism*; D011700:Putrescine / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects* / Q000378:metabolism; D013095:Spermidine / Q000378:metabolism; D013096:Spermine / Q000378:metabolism; D013312:Stress, Physiological; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology*; D000097667:Polyamine Oxidase
chemical_list: D000612:4-Aminobutyrate Transaminase; D012437:Adenosylmethionine Decarboxylase; D006631:Amine Oxidase (Copper-Containing); D017610:Calcium Compounds; D009566:Nitrates; D009955:Ornithine Decarboxylase; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010940:Plant Proteins; D011073:Polyamines; D011700:Putrescine; D013095:Spermidine; D013096:Spermine; D005680:gamma-Aminobutyric Acid; D000097667:Polyamine Oxidase; C059948:calcium nitrate
keywords: Ca(NO(3))(2) stress; Muskmelon; Polyamine; γ-Aminobutyric acid