scholarly journals Suppression of Shade- or Heat-induced Leaf Senescence in Creeping Bentgrass through Transformation with the ipt Gene for Cytokinin Synthesis

2009 ◽  
Vol 134 (6) ◽  
pp. 602-609 ◽  
Author(s):  
Jinpeng Xing ◽  
Yan Xu ◽  
Jiang Tian ◽  
Thomas Gianfagna ◽  
Bingru Huang
Keyword(s):  
Heat Stress ◽  
Chlorophyll Content ◽  
Leaf Senescence ◽  
Creeping Bentgrass ◽  
Grass Species ◽  
Control Line ◽  
Dark Treatment ◽  
Transgenic Lines ◽  
Cytokinin Synthesis ◽  
Whole Plants

Cytokinins have been associated with delaying or suppressing leaf senescence in plants. The objectives of this study were to determine whether the expression of the ipt gene that encodes adenine isopentenyltransferase would delay leaf senescence induced by shade or heat stress in a perennial grass species. Creeping bentgrass (Agrostis stolonifera cv. Penncross) was transformed with ipt isolated from agrobacterium (Agrobacterium tumefaciens) using two gene constructs (SAG12-ipt and HSP18-ipt) designed to activate cytokinin synthesis during shade or heat stress. Whole plants of nine SAG12-ipt transgenic lines and the nontransgenic control plants were incubated in darkness at 20 °C for 20 days. Chlorophyll content of all transgenic lines and the control line decreased after dark treatment, but the decline was less pronounced in transgenic lines. All transgenic lines had higher isopentenyladenine (iP/iPA) content than the control line after 20 days of treatment. In six of the transgenic lines, iP/iPA content remained the same or higher after dark treatment. Whole plants of nine HSP18-ipt transgenic lines and the control plants were incubated at 35 °C for 7 days. Chlorophyll and iP/iPA content declined in the control plants, but the nine transgenic lines had a significantly higher concentration of iP/iPA and were able to maintain chlorophyll content at the prestress level. Our results suggest that expression of SAG12-ipt or HSP18-ipt in creeping bentgrass resulted in increases in cytokinin production, which may have led to the delay and suppression of leaf senescence induced by shade or heat stress.

scholarly journals Chitosan (CTS) Alleviates Heat-Induced Leaf Senescence in Creeping Bentgrass by Regulating Chlorophyll Metabolism, Antioxidant Defense, and the Heat Shock Pathway

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5337
Author(s):  
Cheng Huang ◽  
Yulong Tian ◽  
Bingbing Zhang ◽  
Muhammad Jawad Hassan ◽  
Zhou Li ◽  
...  
Keyword(s):  
Heat Stress ◽  
Heat Shock ◽  
Leaf Senescence ◽  
Heat Tolerance ◽  
Antioxidant Defense ◽  
Creeping Bentgrass ◽  
Grass Species ◽  
Antioxidant Enzyme Activities ◽  
Ros Scavenging ◽  
Chlorophyll Metabolism

Chitosan (CTS) is a deacetylated derivative of chitin that is involved in adaptive response to abiotic stresses. However, the regulatory role of CTS in heat tolerance is still not fully understood in plants, especially in grass species. The aim of this study was to investigate whether the CTS could reduce heat-induced senescence and damage to creeping bentgrass associated with alterations in antioxidant defense, chlorophyll (Chl) metabolism, and the heat shock pathway. Plants were pretreated exogenously with or without CTS (0.1 g L−1) before being exposed to normal (23/18 °C) or high-temperature (38/33 °C) conditions for 15 days. Heat stress induced detrimental effects, including declines in leaf relative water content and photochemical efficiency, but significantly increased reactive oxygen species (ROS) accumulation, membrane lipid peroxidation, and Chl loss in leaves. The exogenous application of CTS significantly alleviated heat-induced damage in creeping bentgrass leaves by ameliorating water balance, ROS scavenging, the maintenance of Chl metabolism, and photosynthesis. Compared to untreated plants under heat stress, CTS-treated creeping bentgrass exhibited a significantly higher transcription level of genes involved in Chl biosynthesis (AsPBGD and AsCHLH), as well as a lower expression level of Chl degradation-related gene (AsPPH) and senescence-associated genes (AsSAG12, AsSAG39, Asl20, and Ash36), thus reducing leaf senescence and enhancing photosynthetic performance under heat stress. In addition, the foliar application of CTS significantly improved antioxidant enzyme activities (SOD, CAT, POD, and APX), thereby effectively reducing heat-induced oxidative damage. Furthermore, heat tolerance regulated by the CTS in creeping bentgrass was also associated with the heat shock pathway, since AsHSFA-6a and AsHSP82 were significantly up-regulated by the CTS during heat stress. The potential mechanisms of CTS-regulated thermotolerance associated with other metabolic pathways still need to be further studied in grass species.

scholarly journals Effects of ipt Gene Expression on Leaf Senescence Induced by Nitrogen or Phosphorus Deficiency in Creeping Bentgrass

2010 ◽  
Vol 135 (2) ◽  
pp. 108-115 ◽  
Author(s):  
Yan Zhang ◽  
Cuiyue Liang ◽  
Yan Xu ◽  
Thomas Gianfagna ◽  
Bingru Huang
Keyword(s):  
Leaf Senescence ◽  
Reductase Activity ◽  
Phosphorus Deficiency ◽  
Perennial Grass ◽  
Photochemical Efficiency ◽  
Creeping Bentgrass ◽  
Essential Elements ◽  
Grass Species ◽  
Control Line ◽  
P Deficiency

The objective of the study was to determine whether the expression of a cytokinin (CK) biosynthesis gene encoding adenine isopentenyl transferase (ipt) would delay or suppress leaf senescence induced by nitrogen (N) or phosphorus (P) deficiency in a C3 grass species, creeping bentgrass (Agrostis stolonifera). The ipt gene was ligated to a senescence-associated promoter, SAG12, and was transferred into creeping bentgrass using an agrobacterium (Agrobacterium tumefaciens)-mediated transformation technique. Plants from an SAG12-ipt transgenic line (S41) and a null transformant (NT) control line were grown in nutrient solutions with all essential elements or without N (−N) or P (−P) for 21 days. Significant declines in leaf photochemical efficiency (Fv/Fm) and chlorophyll content of mature leaves were detected in NT and SAG12-ipt plants exposed to N or P deficiency. Compared to the NT control line, SAG12-ipt plants had higher levels of Fv/Fm, chlorophyll, and CK contents in leaves, and these differences between the NT control and SAG12-ipt line became more pronounced with treatment duration. The ipt expression was detected in the −P-treated and the −N-treated plants after 21 days, although the level of expression decreased under N or P deficiency. Under −P treatment, root acid phosphatase activity was greater in SAG12-ipt line than in the NT control line. No significant differences in nitrate reductase activity were detected in leaves or roots between the SAG12-ipt and the NT control lines. Our results demonstrated that SAG12-ipt expression suppressed leaf senescence induced by N or P deficiency in a perennial grass species. The suppressing effects on leaf senescence under P deficiency may be related to CK regulation of more efficient use of P in roots of the SAG12-ipt plants.

scholarly journals GmNAC81 Inversely Modulates Leaf Senescence and Drought Tolerance

2020 ◽  
Vol 11 ◽  
Author(s):  
Dalton O. Ferreira ◽  
Otto T. Fraga ◽  
Maiana R. Pimenta ◽  
Hanna D. N. Caetano ◽  
João Paulo B. Machado ◽  
...  
Keyword(s):  
Cell Death ◽  
Drought Tolerance ◽  
Leaf Senescence ◽  
Control Line ◽  
Aba Signaling ◽  
Downstream Effector ◽  
Relative Water ◽  
Cell Death Program ◽  
Transgenic Lines ◽  
Increased Sensitivity

Glycine max NAC81 (GmNAC81) is a downstream effector of the DCD/NRP-mediated cell death signaling, which interacts with GmNAC30 to fully induce the caspase 1-like vacuolar processing enzyme (VPE) expression, the executioner of the cell death program. GmNAC81 has been previously shown to positively modulate leaf senescence via the NRP/GmNAC81/VPE signaling module. Here, we examined the transcriptome induced by GmNAC81 overexpression and leaf senescence and showed that GmNAC81 further modulates leaf senescence by regulating an extensive repertoire of functionally characterized senescence-associated genes (SAGs). Because the NRP/GmNAC81/VPE signaling circuit also relays stress-induced cell death signals, we examined the effect of GmNAC81 overexpression in drought responses. Enhanced GmNAC81 expression in the transgenic lines increased sensitivity to water deprivation. Under progressive drought, the GmNAC81-overexpressing lines displayed severe leaf wilting, a larger and faster decline in leaf Ψw, relative water content (RWC), photosynthesis rate, stomatal conductance, and transpiration rate, in addition to higher Ci/Ca and lower Fm/Fv ratios compared to the BR16 control line. Collectively, these results indicate that the photosynthetic activity and apparatus were more affected by drought in the transgenic lines. Consistent with hypersensitivity to drought, chlorophyll loss, and lipid peroxidation were higher in the GmNAC81-overexpressing lines than in BR16 under dehydration. In addition to inducing VPE expression, GmNAC81 overexpression uncovered the regulation of typical drought-responsive genes. In particular, key regulators and effectors of ABA signaling were suppressed by GmNAC81 overexpression. These results suggest that GmNAC81 may negatively control drought tolerance not only via VPE activation but also via suppression of ABA signaling.

scholarly journals Sitosterol-mediated Antioxidant Regulation to Enhance Heat Tolerance in Creeping Bentgrass

2022 ◽  
Vol 147 (1) ◽  
pp. 18-24
Author(s):  
Stephanie Rossi ◽  
Bingru Huang
Keyword(s):  
Heat Stress ◽  
Leaf Senescence ◽  
Heat Tolerance ◽  
Foliar Application ◽  
Creeping Bentgrass ◽  
Membrane Lipid ◽  
Membrane Stability ◽  
Turf Quality ◽  
Mda Content ◽  
Plant Metabolite

Heat stress symptoms in cool-season plants are characterized by loss of chlorophyll (Chl) and membrane stability, as well as oxidative damage. The objectives of this study were to determine whether foliar application of β-sitosterol, a naturally occurring plant metabolite, may promote heat tolerance by suppressing heat-induced leaf senescence as indicated by the maintenance of healthy turf quality (TQ), and Chl and membrane stability; and to determine its roles in regulating antioxidant metabolism in creeping bentgrass (Agrostis stolonifera). ‘Penncross’ plants were exposed to heat stress (35/30 °C day/night) optimal temperature conditions (nonstressed control, 22/17 °C day/night) for a duration of 28 days in environment-controlled growth chambers. Plants were foliar-treated with β-sitosterol (400 µM) or water only (untreated control) before heat stress, and at 7-day intervals through 28 days of heat stress. Plants treated with β-sitosterol had significantly greater TQ and Chl content, and significantly less electrolyte leakage (EL) than untreated controls at 21 and 28 days of heat stress. Application of β-sitosterol reduced malondialdehyde (MDA) content significantly at 21 and 28 days of heat stress, and promoted the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) from 14 through 28 days of heat stress. β-Sitosterol effectively improved heat tolerance through suppression of leaf senescence in creeping bentgrass exposed to heat stress in association with the alleviation of membrane lipid peroxidation and activation of the enzymatic antioxidant system.

scholarly journals Responses of Creeping Bentgrass to Trinexapac-ethyl and Biostimulants under Summer Stress

HortScience ◽  
2010 ◽  
Vol 45 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Yan Xu ◽  
Bingru Huang
Keyword(s):  
Root Growth ◽  
Chlorophyll Content ◽  
Foliar Application ◽  
Sandy Loam ◽  
Creeping Bentgrass ◽  
Control Treatment ◽  
Grass Species ◽  
Water Control ◽  
Turf Quality ◽  
Putting Green

Summer decline in turf quality and growth of cool-season grass species is a major concern in turfgrass management. The objectives of this study were to investigate whether foliar application of trinexapac-ethyl (TE) and two biostimulants (TurfVigor and CPR) containing seaweed extracts would alleviate the decline in creeping bentgrass (Agrostis stolonifera L.) growth during summer months and to examine effects of TE and the biostimulants on leaf senescence and root growth. The study was performed on a ‘Penncross’ putting green built on a sandy loam soil at Hort Farm II, North Brunswick, NJ, in 2007 and 2008. Turf was foliar-sprayed with water (control), TE (0.05 kg a.i./ha), TurfVigor (47.75 L·ha−1), or CPR (19.10 L·ha−1) from late June to early September in a 2-week interval in both years. Turf quality, density, chlorophyll content, canopy photosynthetic rate (Pn), and root growth exhibited significant decline during July and August in both 2007 and 2008, to a greater extent in each parameter for the control treatment. Foliar application of TE resulted in significant improvement in turf quality, density, chlorophyll content, and Pn on certain sampling dates from July to September in both years compared with the control. Both TurfVigor and CPR significantly improved visual quality during July and August in both years by promoting both shoot and root growth. This study suggests that proper application of TE and selected biostimulants could be effective to improve summer performance of creeping bentgrass.

scholarly journals Heat-induced Leaf Senescence and Hormonal Changes for Thermal Bentgrass and Turf-type Bentgrass Species Differing in Heat Tolerance

2007 ◽  
Vol 132 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Yan Xu ◽  
Bingru Huang
Keyword(s):  
Heat Stress ◽  
High Temperature ◽  
Leaf Senescence ◽  
Heat Tolerance ◽  
Photochemical Efficiency ◽  
Creeping Bentgrass ◽  
Zeatin Riboside ◽  
Hormonal Changes ◽  
Heat Tolerant ◽  
Aba Content

Leaf senescence can be induced by many environmental stresses, including supraoptimal temperatures. The objectives of this study were to evaluate leaf senescence induced by heat stress for two Agrostis species contrasting in heat tolerance and to examine whether heat-induced leaf senescence in both species was associated with changes in three major senescence-related hormones: ethylene, abscisic acid (ABA), and cytokinins. Plants of heat-tolerant rough bentgrass (Agrostis scabra Willd.) and heat-sensitive creeping bentgrass (Agrostis stolonifera L.) were exposed to 35/30 °C (day/night) (high temperature) or 20/15 °C (control) for 35 d in growth chambers. Turf quality, photochemical efficiency (Fv/Fm), and the contents of two pigments (chlorophyll and carotenoid) for both species decreased under high temperature; however, heat-tolerant A. scabra exhibited delayed and less severe decline in all parameters compared with heat-sensitive A. stolonifera. Ethylene production rate increased in both species at 35 °C, but the increase was observed 21 days later in A. scabra compared with that in A. stolonifera. ABA content increased at the initiation of heat stress and then declined in both species after prolonged heat stress. However, the timing of the increase was delayed for 7 days and the highest level of ABA content was less in A. scabra (4.0 times that of the control) than that in A. stolonifera (5.9 times that of the control). Decreases in both forms of cytokinins (transzeatin/zeatin riboside and isopentenyl adenosine) were also delayed for 14 days and less pronounced in A. scabra. Correlation analysis revealed that leaf senescence induced by heat stress was negatively correlated to ethylene and ABA accumulation and positively correlated to cytokinin production. Delayed leaf senescence in A. scabra under heat stress could be related to slower and less magnitude of changes in ethylene, ABA, and cytokinins.

scholarly journals Effects of SAG12-ipt and HSP18.2-ipt Expression on Cytokinin Production, Root Growth, and Leaf Senescence in Creeping Bentgrass Exposed to Drought Stress

2010 ◽  
Vol 135 (3) ◽  
pp. 230-239 ◽  
Author(s):  
Emily B. Merewitz ◽  
Thomas Gianfagna ◽  
Bingru Huang
Keyword(s):  
Drought Stress ◽  
Root Growth ◽  
Leaf Senescence ◽  
Photochemical Efficiency ◽  
Creeping Bentgrass ◽  
Growth Responses ◽  
Turf Quality ◽  
Relative Water ◽  
Transgenic Lines ◽  
Leaf Relative Water Content

Drought stress is a widespread abiotic stress that causes a decline in plant growth. Drought injury symptoms have been associated with an inhibition in cytokinin (CK) synthesis. The objectives of this study were to investigate whether expression of a gene (ipt) encoding the enzyme adenine isopentenyl phosphotransferase for CK synthesis ligated to a senescence-activated promoter (SAG12) or a heat shock promoter (HSP18.2) would improve drought tolerance in creeping bentgrass (Agrostis stolonifera) and to examine shoot and root growth responses to drought stress associated with changes in endogenous production of CK, and the proportional change in CK and abscisic acid (ABA) due to ipt transformation. Most SAG12-ipt and HSP18.2-ipt transgenic lines exhibited significantly higher turf quality, photochemical efficiency, chlorophyll content, leaf relative water content, and root:shoot ratio under drought stress than the null transformant or the wild-type ‘Penncross’ plants. Transgenic lines that had better growth and turf performance generally had higher CK content and a higher CK-to-ABA ratio, although the direct correlation of CK and ABA content with individual physiological parameters in individual lines was not clear. Our results demonstrated that expressing ipt resulted in the improvement of turf performance under drought stress in creeping bentgrass in some of the transgenic plants with SAG12-ipt or HSP18.2-ipt, which could be associated with the suppression of leaf senescence and promoting root growth relative to shoot growth due to the maintenance of higher CK level and a higher ratio of CK to ABA.

scholarly journals Leaf Senescence and Protein Metabolism in Creeping Bentgrass Exposed to Heat Stress and Treated with Cytokinins

2007 ◽  
Vol 132 (4) ◽  
pp. 467-472 ◽  
Author(s):  
Mahalaxmi Veerasamy ◽  
Yali He ◽  
Bingru Huang
Keyword(s):  
Heat Stress ◽  
Protein Content ◽  
Leaf Senescence ◽  
Protein Metabolism ◽  
Soluble Protein ◽  
Protease Activity ◽  
Creeping Bentgrass ◽  
Zeatin Riboside ◽  
Soluble Protein Content ◽  
Leaf Chlorophyll

Heat stress induces leaf senescence and causes changes in protein metabolism. The objective of this study was to investigate effects of exogenous application of a synthetic form of cytokinin, zeatin riboside (ZR), on protein metabolism associated with leaf senescence under heat stress for a cool-season grass species. Creeping bentgrass (Agrostis stolonifera L.) (cv. Penncross) plants were exposed to optimum temperature control (20/15 °C, day/night) and heat stress (35/30 °C) in growth chambers. Before heat stress treatments, foliage was sprayed with 10 μmol ZR or water (untreated) for 3 days and then once per week during 35 days of heat stress. Leaf chlorophyll content, photochemical efficiency (Fv/Fm), and soluble protein content declined, whereas protease activity increased during heat stress. Treatments with ZR helped maintain higher leaf chlorophyll content, Fv/Fm, and soluble protein content under heat stress. Protease activity in ZR-treated plants was lower than that of untreated plants. Zeatin riboside-treated plants had less severe degradation of ribulose-1,5-bisphosphate carboxylase proteins than untreated plants exposed to heat stress. In addition, ZR treatment upregulated the expression of 32- and 57-kDa proteins under heat stress conditions. These results demonstrated that the exogenous application of ZR ameliorated the negative effects of heat stress, as manifested by suppression or delay of leaf senescence. Cytokinins may have helped to alleviate heat stress injury, probably by slowing down the action of protease and by induction or upregulation of heat-shock proteins.

scholarly journals STAYGREEN-mediated chlorophyll a catabolism is critical for photosystem stability upon heat stress in ryegrass

2021 ◽  
Author(s):  
Jing Zhang ◽  
Hui Li ◽  
Xinru Huang ◽  
Jing Xing ◽  
Jiaming Yao ◽  
...  
Keyword(s):  
Heat Stress ◽  
Leaf Senescence ◽  
Heat Tolerance ◽  
Perennial Ryegrass ◽  
System Stability ◽  
Ros Generation ◽  
Stay Green ◽  
Chl A ◽  
Transgenic Lines

Chlorophyll (Chl) loss is one of the most visible symptoms of heat-induced leaf senescence, especially for cool-season grass species. Suppression of the Chl a Me-dechelatase gene, SGR (also named as nye1), blocked the degradation of Chl a and resulted in the 'stay-green' trait during leaf senescence. However, effect of Chl a catabolism on plant tolerance to long-term moderate heat stress (35-40?) remains unclear. In this study, we suppressed the expression of Chl a catabolic gene, LpSGR, in both constitutive and inducible manners in perennial ryegrass. Constitutive suppression of LpSGR aggravated heat stress-induced chloroplast structure and photosystem damages, disrupted energy utilization/dissipation during photosynthesis, activated ROS generation with weakened ROS-scavenging enzyme activities. Transcriptome comparison among wildtype (WT) and transgenic RNAi plants under either the optimum or high temperature conditions also emphasized the effect of Chl a catabolism on expression of genes encoding photosynthesis system, ROS-generation and scavenging system, and heat shock transcription factors. Furthermore, making use of a modified ethanol-inducible system, we generated stable transgenic perennial ryegrass to suppress LpSGR in an inducible manner. Without ethanol induction, these transgenic lines exhibited the same growth and heat tolerance traits to WT, while under the induction of ethanol spray, the transgenic lines also showed compromised heat tolerance. Taken together, our data suggest that Chl a catabolism is critical for energy dissipation and electron transfer in photosynthesis, ROS-balancing and chloroplast membrane system stability upon long-term moderate heat stress.

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