Constitutive Expression of a Tomato Small Heat Shock Protein Gene LeHSP21 Improves Tolerance to High-Temperature Stress by Enhancing Antioxidation Capacity in Tobacco
Abstract:It is well established that small heat shock proteins (sHSPs) play an important role in thermotolerance in various organisms due to their abundance and diversity. In the present study, a chloroplast small heat shock protein gene (LeHSP21) from tomato (Lycopersicon esculentum cv PKM-1) was constitutively expressed in tobacco (Nicotiana tabacum L. cv Wisconsin 38) plants via Agrobacterium-mediated transformation. When compared to wild-type control plants, transgenic tobacco plants constitutively expressing LeHSP… Show more
“…Upon treatment with drought or salt stress, proline accumulated to a significantly higher level in both 35S:: ZmmiR156 and Rab17::MIR156 transgenic plants than in wild type and vector control plants (Figures 2E, 3E, and 4D, I). This is consistent with previous reports that transgenic salt tolerant plants accumulated more proline (Nanjo et al, 1999;Zhang and Blumwald, 2001;Zhang et al, 2016). Therefore, the augmented proline accumulation in transgenic plants may have helped protect the activity of antioxidative enzymes and as a result alleviated the adverse impacts imposed by drought and salt on transgenic plants.…”
Section: Discussionsupporting
confidence: 92%
“…Therefore, we postulated that under adverse growth conditions, expression of ZmmiR156 helped protect cell membrane integrity in transgenic plants. This hypothesis was also supported by the observations of transgenic tobacco expressing inositol polyphosphate 6-/3kinase AtIpk2b and heat shock protein LeHSP21 (Yang et al, 2008;Zhang et al, 2016).…”
Plants in the juvenile state are more tolerant to adverse conditions. Constitutive expression of MicroRNA156 (miR156) prolonged the juvenile phase and increased resistance to abiotic stress, but also affected the architecture of transgenic plants. In this study, we investigated the possibility of subtle manipulation of miR156 expression in flowering plants, with the goal to increase tolerance to abiotic stress without altering the normal growth and development of transgenic plants. Transgenic tobacco plants expressing ZmmiR156 from maize were generated, driven either by the cauliflower mosaic virus (CaMV) 35S promoter or the stress-inducible ZmRab17 promoter. Expression of ZmmiR156 led to improved drought and salt tolerance in both 35S::MIR156 and Rab17::MIR156 transgenic plants, as shown by more vigorous growth, greater biomass production and higher antioxidant enzyme expression after a long period of drought or salt treatment, when compared to wild type and transgenic vector control plants. However, constitutive expression of ZmmiR156 also resulted in retarded growth, increased branching and delayed flowering of transgenic plants. These undesirable developmental changes could be mitigated by using the stress-inducible ZmRab17 promoter. Furthermore, under drought or salt stress conditions, expression of ZmmiR156 reduced the transcript level of NtSPL2 and NtSPL9, the genes potentially targeted by ZmmiR156, as well as that of CP1, CP2, and SAG12, the senescenceassociated genes in tobacco. Collectively, our results indicate that ZmmiR156 can be temporally manipulated for the genetic improvement of plants resistant to various abiotic stresses.
“…Upon treatment with drought or salt stress, proline accumulated to a significantly higher level in both 35S:: ZmmiR156 and Rab17::MIR156 transgenic plants than in wild type and vector control plants (Figures 2E, 3E, and 4D, I). This is consistent with previous reports that transgenic salt tolerant plants accumulated more proline (Nanjo et al, 1999;Zhang and Blumwald, 2001;Zhang et al, 2016). Therefore, the augmented proline accumulation in transgenic plants may have helped protect the activity of antioxidative enzymes and as a result alleviated the adverse impacts imposed by drought and salt on transgenic plants.…”
Section: Discussionsupporting
confidence: 92%
“…Therefore, we postulated that under adverse growth conditions, expression of ZmmiR156 helped protect cell membrane integrity in transgenic plants. This hypothesis was also supported by the observations of transgenic tobacco expressing inositol polyphosphate 6-/3kinase AtIpk2b and heat shock protein LeHSP21 (Yang et al, 2008;Zhang et al, 2016).…”
Plants in the juvenile state are more tolerant to adverse conditions. Constitutive expression of MicroRNA156 (miR156) prolonged the juvenile phase and increased resistance to abiotic stress, but also affected the architecture of transgenic plants. In this study, we investigated the possibility of subtle manipulation of miR156 expression in flowering plants, with the goal to increase tolerance to abiotic stress without altering the normal growth and development of transgenic plants. Transgenic tobacco plants expressing ZmmiR156 from maize were generated, driven either by the cauliflower mosaic virus (CaMV) 35S promoter or the stress-inducible ZmRab17 promoter. Expression of ZmmiR156 led to improved drought and salt tolerance in both 35S::MIR156 and Rab17::MIR156 transgenic plants, as shown by more vigorous growth, greater biomass production and higher antioxidant enzyme expression after a long period of drought or salt treatment, when compared to wild type and transgenic vector control plants. However, constitutive expression of ZmmiR156 also resulted in retarded growth, increased branching and delayed flowering of transgenic plants. These undesirable developmental changes could be mitigated by using the stress-inducible ZmRab17 promoter. Furthermore, under drought or salt stress conditions, expression of ZmmiR156 reduced the transcript level of NtSPL2 and NtSPL9, the genes potentially targeted by ZmmiR156, as well as that of CP1, CP2, and SAG12, the senescenceassociated genes in tobacco. Collectively, our results indicate that ZmmiR156 can be temporally manipulated for the genetic improvement of plants resistant to various abiotic stresses.
“…High temperature at three reproductive stages of cotton increased ROS e.g. lipid membrane peroxidation contents (MDA) which may affect the cell organelles as documented by 25 . A constricted balance between ROS and antioxidant enzymes is required 26 , 27 but the stress conditions affected this balance between chloroplasts or mitochondria.…”
Section: Discussionmentioning
confidence: 97%
“…The present findings were supported by 4 , 28 . High temperature stress reduced chlorophyll contents and photosynthetic rate in tomato leaves 25 which might be due to reduced CO 2 fixation and photosynthesis process 29 , 30 . Relatively lower chlorophyll contents and net photosynthetic rate was observed in sub and supra-optimal thermal regimes of glass house and under high temperature regimes of field study at three reproductive stages of cotton crop might be due to higher oxidative stress.…”
Episodes of extremely high temperature during reproductive stages of cotton crops are common in many parts of the world. Heat stress negatively influences plant growth, physiology and ultimately lint yield. This study attempts to modulate heat-induced damage to cotton crops via application of growth regulators e.g. hydrogen peroxide (H2O2 30ppm), salicylic acid (SA 50ppm), moringa leaf extract (MLE 30 times diluted) and ascorbic acid (ASA 70ppm). Cotton plants were exposed to different thermal regimes by staggering sowing time (field) or exposing to elevated temperatures (38/24 °C and 45/30 °C) for one week during reproductive growth stages (glasshouse). Elevated temperatures significantly induced lipid membrane damage, which was evident from an increased malondialdehyde (MDA) level in cotton leaves. Heat-stressed plants also experienced a significant reduction in leaf chlorophyll contents, net photosynthetic rate and lint yield. Hydrogen peroxide outclassed all the other regulators in increasing leaf SOD, CAT activity, chlorophyll contents, net photosynthetic rate, number of sympodial branches, boll weight and fiber quality components. For example, hydrogen peroxide improved boll weight of heat stressed plants by 32% (supra), 12% (sub) under glasshouse and 18% (supra) under field conditions compared with water treated plants under the same temperatures. Growth regulators, specifically, H2O2 protected physiological processes of cotton from heat-induced injury by capturing reactive oxygen species and modulating antioxidant enzymes. Thus, cotton performance in the future warmer climates may be improved through regulation (endogenous) or application (exogenous) hormones during reproductive phases.
“…To date, the Hsp20 gene families have been investigated in several plant species, including Arabidopsis , rice, soybean, pepper, and Populus trchocarpa (Scharf et al, 2001 ; Waters et al, 2008 ; Ouyang et al, 2009 ; Sarkar et al, 2009 ; Lopes-Caitar et al, 2013 ; Guo et al, 2015 ). In addition, some key features of Hsp20 and biologic function of several Hsp20 genes had been identified (Nautiyal and Shono, 2010 ; Goyal et al, 2012 ; Huther et al, 2013 ; Mahesh et al, 2013 ; Arce et al, 2015 ; Zhang et al, 2016 ). Although the availability of the tomato whole-genome sequence provides valuable resources for getting into an in-depth understanding of Hsp20s (Sato et al, 2012 ), little information is available on the integrated Hsp20 family at whole genomic level in tomato.…”
The Hsp20 genes are involved in the response of plants to environment stresses including heat shock and also play a vital role in plant growth and development. They represent the most abundant small heat shock proteins (sHsps) in plants, but little is known about this family in tomato (Solanum lycopersicum), an important vegetable crop in the world. Here, we characterized heat shock protein 20 (SlHsp20) gene family in tomato through integration of gene structure, chromosome location, phylogenetic relationship, and expression profile. Using bioinformatics-based methods, we identified at least 42 putative SlHsp20 genes in tomato. Sequence analysis revealed that most of SlHsp20 genes possessed no intron or a relatively short intron in length. Chromosome mapping indicated that inter-arm and intra-chromosome duplication events contributed remarkably to the expansion of SlHsp20 genes. Phylogentic tree of Hsp20 genes from tomato and other plant species revealed that SlHsp20 genes were grouped into 13 subfamilies, indicating that these genes may have a common ancestor that generated diverse subfamilies prior to the mono-dicot split. In addition, expression analysis using RNA-seq in various tissues and developmental stages of cultivated tomato and the wild relative Solanum pimpinellifolium revealed that most of these genes (83%) were expressed in at least one stage from at least one genotype. Out of 42 genes, 4 genes were expressed constitutively in almost all the tissues analyzed, implying that these genes might have specific housekeeping function in tomato cell under normal growth conditions. Two SlHsp20 genes displayed differential expression levels between cultivated tomato and S. pimpinellifolium in vegetative (leaf and root) and reproductive organs (floral bud and flower), suggesting inter-species diversification for functional specialization during the process of domestication. Based on genome-wide microarray analysis, we showed that the transcript levels of SlHsp20 genes could be induced profusely by abiotic and biotic stresses such as heat, drought, salt, Botrytis cinerea, and Tomato Spotted Wilt Virus (TSWV), indicating their potential roles in mediating the response of tomato plants to environment stresses. In conclusion, these results provide valuable information for elucidating the evolutionary relationship of Hsp20 gene family and functional characterization of the SlHsp20 gene family in the future.
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