Upregulation of Phosphatidylinositol 3-Kinase (PI3K) Enhances Ethylene Biosynthesis and Accelerates Flower Senescence in Transgenic Nicotiana tabacum L.

Abstract

Phosphatidylinositol 3-kinase (PI3K) is a key enzyme that phosphorylates phosphatidylinositol at 3’-hydroxyl position of the inositol head group initiating the generation of several phosphorylated phosphatidylinositols, collectively referred to as phosphoinositides. The function of PI3K in plant senescence and ethylene signal transduction process was studied by expression of Solanum lycopersicum PI3K in transgenic Nicotiana tabacum, and delineating its effect on flower senescence. Detached flowers of transgenic tobacco plants with overexpressed Sl-PI3K (OX) displayed accelerated senescence and reduced longevity, when compared to the flowers of wild type plants. Flowers from PI3K-overexpressing plants showed enhanced ethylene production and upregulated expression of 1-aminocyclopropane-1-carboxylic acid oxidase 1 (ACO1). Real time polymerase chain reaction (PCR) analysis showed that PI3K was expressed at a higher level in OX flowers than in the control. Seedlings of OX-lines also demonstrated a triple response phenotype with characteristic exaggerated apical hook, shorter hypocotyls and increased sensitivity to 1-aminocyclopropane-1-carboxylate than the control wild type seedlings. In floral tissue from OX-lines, Solanum lycopersicum phosphatidylinositol 3-kinase green fluorescent protein (PI3K-GFP) chimera protein was localized primarily in stomata, potentially in cytoplasm and membrane adjacent to stomatal pores in the guard cells. Immunoblot analysis of PI3K expression in OX lines demonstrated increased protein level compared to the control. Results of the present study suggest that PI3K plays a crucial role in senescence by enhancing ethylene biosynthesis and signaling.

Adenine type and diphenyl urea derived cytokinins improve the postharvest performance of Iris germanica L. cut scapes

“…Decreased LOX activity resulted in the decreased lipid peroxidation which can be visualized by the increased membrane stability index in the tissue samples from cytokinin treated scapes. This decrease in the LOX activity and LPO by cytokinin treatment can be attributed to maintenance of adequate phospholipids, proteins and thiols by preventing the leakage of proteases from vacuoles into the cytoplasm (Fukuchi-Mizutani et al 2000;Pak and van Doorn 2005;Liu et al 2016b;Dek et al 2017).…”

“…Cytokinins have been found to delay senescence either by increasing the production of ROS scavenging enzymes (through its positive effect on protein synthesis) or directly by scavenging the free radicals (Synkova et al 2006;Lattanzio et al 2006;Liu et al 2016a). Cytokinins have also been found to slow down the process of free radical formation during senescence in tobacco plant (Synkova et al 2006;Ahmad and Tahir 2016b;Dek et al 2017). POD, SOD and CAT activity was found to be modulated by the application of cytokinins for efficient scavenging of the reactive oxygen species (Petit-Paly et al 1999, Mwangi et al 2003Mittler et al 2004;Danilova et al 2017).…”

Transcriptome Analysis of Gene Expression Patterns Potentially Associated with Premature Senescence in Nicotiana tabacum L.

“…Recently, Dek reported that there was a decrease in cytokinins and an increase in ABA at postharvest leaves, nevertheless increasing ABA concentration could suppress postharvest senescence [ 19 ]. Phosphatidylinositol 3-kinase (PI3K), a key enzyme of phosphorylating phosphatidylinositol, induced senescence by enhancing ethylene biosynthesis and signaling [ 20 ]. The mitochondrial AAA-protease gene FtSH4 could control the SA synthesis and signaling in senescence via modifying the ROS level and WRKY transcription factors [ 21 ].…”

6-Benzylamino purine outperforms Kinetin and Thidiazuron in ameliorating flower longevity in Calendula officinalis L. by orchestrating physiological and biochemical responses

“…Against to this, BAP was highly effective in maintaining a decreased LOX activity in flowers followed by TDZ and KN, which prevented the excessive lipid peroxidation of the membranes as evident from increased MSI values in the tissue samples. The reduced LOX activity resulted in maintenance of adequate phospholipids, proteins and thiols by preventing the seepage of proteases from vacuoles into the cytoplasm (Macnish et al, 2010;Liu et al, 2016a;Dek et al, 2017). Cytokinin mediated enhanced membrane integrity can also be attributed to its involvement in maintenance of high water content, antioxidant system and reduced peroxidation rates in tissues, which are greatly affected by the stresses like senescence (Ahmad et al, 2018;Honig et al, 2018).…”

“…Petals with decreased APX activity has been found to show early senescence symptoms in various flowers like daylily, gladiolus and carnation by generation and accumulation of ROS (Mittler et al, 2004;Saeed et al, 2014). Exogenous application of cytokinins effectively reduced the free radical formation in tobacco plant during senescence (Dek et al, 2017). The role of cytokinins in maintaining the ambient levels of antioxidant enzymes for longer vase life of the flowers has also been demonstrated by application of cytokinin oxidase inhibitors in wall flowers (Bartrina et al, 2017).…”