Salicylic Acid and H 2 O 2 Induce PPO Derived GUS Expression in Arabidopsis
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Salicylic Acid and H2O2 Induce PPO Derived GUS Expression in Arabidopsis D. Saleema, Z. Zuhraa, W. Akhtarb, H. Koiwac, and T. Mahmooda, * a
Department of Plant Sciences, Quaid-i-Azam University Islamabad, 45320 Pakistan of Botany, University of Azad Jammu and Kashmir Muzaffarabad, Muzaffarabad, 13100 Pakistan c Department of Horticultural Sciences, Texas A&M University, College Station, TX77843-2133 USA *e-mail: [email protected]
bDepartment
Received October 7, 2019; revised February 9, 2020; accepted February 19, 2020
Abstract—Polyphenol oxidases (PPOs) are ubiquitous enzymes of plant defense which transform polyphenols into quinones that response to biotic and abiotic stresses. Transgenic Arabidopsis thaliana (L.) Heynh. lines harboring OsPPO promoter fused to β-glucoronidase (GUS) reporter gene, were treated exogenously with 0.1, 0.5 and 1 mM concentrations of salicylic acid (SA) and 5, 10 and 15 mM of hydrogen peroxide (H2O2). Plant samples were harvested after 1, 3 and 5 days of treatment. Transcriptional profiling of OsPPOGUS by qRT-PCR revealed the highest 12.96-fold induction with 0.5 mM SA after 3 days of treatment and the lowest fold induction (0.57) with 1 mM SA after one day. With H2O2, the OsPPOGUS mRNA transcript showed the highest accumulation of 21.08-fold change with 10 mM after 5 days of treatment and the lowest induction (3-fold) after 1 day of treatment by 15 mM H2O2. This specific OsPPO induction in response to SA and H2O2 clearly links OsPPO in potential responses to such stressors. Keywords: Arabidopsis thaliana, OsPPO, signaling molecules, salicylic acid, hydrogen peroxide, OsPPO induction, qRT-PCR, OsPPOGUS DOI: 10.1134/S1021443720050131
INTRODUCTION PPOs are widely distributed among bacteria, fungi and plants with high diversity among land plants. Many of PPO genes are found in all plant species except Arabidopsis [1]. PPO gene system originated in bacteria, transferred and expanded through duplication or lost by rearrangement or deletion of chromosomal fragment during evolution leading to considerable variation in numbers of PPO gene among land plants. The loss of PPO gene in Arabidopsis might happened by mutation and deletion during chromosomal rearrangements [2]. Absence of PPO gene in Arabidopsis is attributed to ecological or physiological adaptation without relating to genome size [1, 3]. PPOs are grouped into catechol oxidases and tyrosinases (belonging to type III copper proteins family) which convert polyphenols into quinones through hydroxylation and oxidation by utilizing molecular oxygen [4]. PPOs are significantly involved in plant growth, reproduction, enzymatic browning and resistance to biotic and abiotic stresses [5]. Defensive role of PPOs can be attributed by the studies of PPO transcripts accumulation in response to wounding, pathogen infestation and plant hormones as SA, methyl jasAbbreviations: GUS—β-glucoronidase; OsPPO—rice polyphenol oxidase; SA—salicylic acid.
monate (MeJ) and systemin [6]. PPOs hinder herbivory and pathogen attacks through t
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