Cloning and characterization of the pepper CaPAO gene for defense responses to salt-induced leaf senescence

Abstract

BackgroundPheophorbide a oxygenase (PAO) is an important enzyme in the chlorophyll catabolism pathway and is involved in leaf senescence. It opens the porphyrin macrocycle of pheophorbide a and finally forms the primary fluorescent chlorophyll catabolite. Previous studies have demonstrated the function of PAO during cell death. However, the characterizaton of PAO during leaf senescence induced by environmental factors is not well understood.MethodsHomology-based cloning and RACE techniques were used to obtain the full-length cDNA of the CaPAO gene. CaPAO expression was determined by quantitative real-time PCR. Function of CaPAO gene were studied using virus-induced gene silencing and transgenic techniques with tobacco plants (Nicotiana tabacum).ResultsA novel PAO gene CaPAO was isolated from pepper (Capsicum annuum L.). The full-length CaPAO cDNA is comprised of 1838 bp, containing an open reading frame of 1614 bp, and encodes a 537 amino acid protein. This deduced protein belongs to the Rieske-type iron-sulfur superfamily, containing a conserved Rieske cluster. CaPAO expression, as determined by quantitative real-time PCR, was higher in leaves than roots, stems and flowers. It was upregulated by abscisic acid, methyl jasmonate and salicylic acid. Moreover, CaPAO was significantly induced by high salinity and osmotic stress treatments and also was regulated by Phytophthora capsici. The virus-induced gene silencing technique was used to silence the CaPAO gene in pepper plants. After 3 days of high salt treatment, the chlorophyll breakdown of CaPAO-silenced pepper plants was retarded. RD29A promoter-inducible expression vector was constructed and transferred into tobacco plant. After 7 days of salt treatment, the leaves of transgenic plants were severely turned into yellow, the lower leaves showed necrotic symptom and chlorophyll content was significantly lower than that in the control plants.ConclusionsThe expression of CaPAO gene was induced in natural senescence and various stresses. The CaPAO gene may be related to defense responses to various stresses and play an important role in salt-induced leaf senescence.

Plant Peroxisomal Polyamine Oxidase: A Ubiquitous Enzyme Involved in Abiotic Stress Tolerance

“…In the case of Capsicum annuum , CaPAO2 and CaPAO4 prefer Spm over Spd [ 48 ], while in the case of Citrus sinensis , all the PAOs, namely CsPAO1, CsPAO2, CsPAO3, CsPAO4, and CsPAO5, prefer Spd over Spm, except CsPAO6, which only acts upon Spm [ 49 ]. The PAO from Nicotiana tabacum (NtPAO) acts upon both Spd and Spm with equal affinity [ 17 ].…”

“…In the case of Citrus sinensis and Camellia sinensis , the PAOs showed more systemic expression. CsPAO1 , CsPAO2 , CsPAO3 , CsPAO5 , and CsPAO6 have been found to be expressed in near equal amounts in roots, stems, leaves, and cotyledon, while CsPAO4 is highly expressed in roots, stems, and leaves, but not in cotyledon [ 48 ]. The PAOs from Camellia sinensis , namely CmPAO2 , CmPAO3 , and CmPAO6 are expressed in all the tissues; however, the expression level of CmPAO6 is relatively very low compared to CmPAO2 and CmPAO3 [ 50 ].…”

Melatonin Pretreatment Confers Heat Tolerance and Repression of Heat-Induced Senescence in Tomato Through the Modulation of ABA- and GA-Mediated Pathways

“…It is projected that global temperatures will increase from 1.8 to 4.0°C by 2100 ( Parry and Pizer, 2007 ). Leaf senescence is a fine-tuned mechanism that is intensely complicated by diverse intrinsic factors, such as cell death ( Ghanem et al, 2012 ), phytohormones ( Zhang and Guo, 2018 ), senescence-associated genes ( Li et al, 2017 ; Xiao et al, 2017 ), transcription factors ( Ma et al, 2018b ), and environmental factors like darkness ( Weaver et al, 1998 ), detachment ( He and Gan, 2002 ), drought ( Lee et al, 2012 ), salinity or alkalinity ( Yang et al, 2011 ; Xiao et al, 2015 ), and high temperature ( Xu and Huang, 2007 ; Zheng et al, 2016 ). The decline in Chl content is the most prominent feature of natural or stress-induced leaf senescence ( Hörtensteiner, 2006 ), which is important for the absorption of light and the redistribution of excitation energy in the photosynthetic electron transport chain ( Grossman et al, 1995 ).…”

Differential gene expression and physiological changes during acute or persistent plant virus interactions may contribute to viral symptom differences

“…The key regulator of Chl degradation is pheophorbide a oxygenase (PAO), which catalyses the cleavage of the porphyrin ring of pheophorbide, resulting in a red Chl catabolite intermediate (RCC), which later degrades in the vacuole (Fig 5A). The level of PAO increases during biotic stresses [40, 41]. As on the microarray chip, we did not find a specific probe for N .…”