PHYSIOLOGICAL AND HEAT SHOCK PROTEIN RESPONSES IN BELL PEPPER PLANTS UNDER HEAT STRESS

Some cucurbit plants (Cucumis sativus L., Cucurbita pepo L., Cucumis melo L. and Citrillus lanatus L.) were used for investigating some physiological changes and protein patterns under heat stress in plants. Leaf samples were exposed tohigh temperatures as follows 35, 40, 45, 50, 55 and 60°C. Percentage of ion leakage, chlorophyll content, leaf relative water content (RWC) and loss of turgidity, total soluble protein (TSP) content and protein profiles were determined in leaf samples kept at each temperature stage for 30 minutes. Ion leakage was increased especially 55 and 60°C in all cucurbits parallel to the temperature increasement. Total chlorophyll content was decreased slightly in both cucumber cultivars, zucchini, in both melon cultivars and watermelon due to high temperatures. The RWC of cucurbits was decreased on the contrary of the loss of turgidity, which was parallel to the increment of temperatures. While the TSP content in cucumber was decreased with temperature increasement, it was not changed in zucchini and watermelon. In melon cultivars TSP was not noticeably changed until 55°C, but significantly decreased at 60°C. When the SDS-PAGE profiles of cucurbits were examined, many protein bands were observed with sizes ranging from 6.5 kDa to 211 kDa.

SummaryThe effects of heat injury induced by long exposures were evaluated in strawberry (Fragaria × ananassa ‘plants’) Camarosa in this study. Seedlings were grown in 14 × 12 cm pots using perlite for three weeks at 25/10°C day/night temperature, and watered daily by modified 1/3 Hoagland nutrient solution. Half of the plants were transferred to a growth chamber with a constant 25°C, 16/8 h (light/dark) photoperiod regime and 1200 lux light intensity for a week to acclimate the plants. Temperature was increased stepwise (5 K per 48 h) to 30, 35, 40°C and finally to 45°C. In addition to others, plants were transferred from the outside to the growth chamber, at each temperature step to impose a heat shock. Leaf relative water content (RWC, %), loss of turgidity, chlorophyll content (Spad value) and heat-stress tolerance (HTS; LT50) were measured in control and stressed plants. Total soluble proteins and total DNA were extracted from the leaves following the above treatments using standard procedures and total protein contents were determined using a Bradford assay. In general, effects of gradual heat stress (GHS) and shock heat stress (SHS) on the variables studied were mostly significant, except for chlorophyll content, while the effect of temperatures was significant for all the variables. Interaction between the heat stress type and temperature treatments was not significant for leaf RWC, loss of turgidity and chlorophyll content. Data also indicated that total protein and DNA contents were changed significantly by heat stress types (GHS and SHS) and/or temperature treatments. The plants exposed to GHS exhibited a significant increase in HST compared with the plants exposed to SHS (LT50 of 41.5°C and 39°C, respectively). Consequently, gradual heat stress increased HST in strawberry leaves. Increased HST may be associated with the accumulation of several heat-stable proteins in GHS plants.

The effects of heat stress on malondialdehid (MDA) content, ascorbic acid (AsA), isoperoxidases, total soluble protein (TSP) and SDS-PAGE protein profiles of small reddish bean (Phaseolus vulgaris L. cv. Keklik) leaves were investigated. For this purpose, the collected leaf samples (preferably the third from the apex) were placed into pyrex tubes with caps closed and incubated in a water bath: after a 30-minutes habituation at 30ºC, to apply heat stress the leaves were subjected to 35, 40, 45, 50, 55 and 60°C with gradual increments every 30-minutes. According to the results, the MDA content increased with escalating temperatures, starting with 40°C. Although there was fluctuation, the AsA content generally decreased with high temperatures. Besides, TSP content decreased after 50°C. Moreover, three asidic and four basic isoperoxidase bands were identified. There was a marked difference at acidic isoperoxidase band intensities under 40 and 45°C heat treatment. Protein bands with molecu1ar weight of approximately 14.5-195 kDa were determined. In conclusion, especially 40°C is critical for small reddish bean plants, besides 40°C and above temperatures causes oxidative stress in small reddish bean plant. Additionally, isoperoxidases and proteins may be an effective mean on heat stress tolerance.

Tomato has been considered as a potential biological production platform for plant-made pharmaceuticals (PMPs). However, information is limited for protein productivity and dynamics in tomato fruit. As part of our PMP production project, total soluble protein (TSP) content of green and red fruits was analyzed for selected six greenhouse cultivars. The six cultivars consisted of various fruit types (including cluster, cherry, mini plum, and grape types) with sizes ranging from 10 to 150 and from 14 to 188 g fresh weight for green and red fruits, respectively. In fruit TSP content per unit dry weight (DW), approximately seven- to eightfold variation was observed among cultivars for both green and red fruits. There was no significant correlation between fruit TSP content per DW and fruit DW or fruit type over the cultivars irrespective of fruit ripening stage, indicating that fruit weight or fruit type of a cultivar cannot be an indicator of the TSP content per DW. There was also an inconsistent trend in differences in fruit TSP content per whole fruit between green and red fruit among cultivars. Our results suggest that a low-yielding cultivar can produce high TSP content per unit ground area resulting from high TSP content per DW in fruit. A background tomato cultivar or genotype candidate for commercial PMP production should thus be selected from among various fruit types considering both yield potential and fruit TSP content.

Phytophthora blight, caused by the oomycete pathogen, Phytophthora capsici, is a devastating disease on bell pepper and cucurbit crops in the United States and worldwide (29,40). P. capsici causes a root and crown rot, as well as an aerial blight of leaves, fruit, and stems, on bell pepper (Capsicum annuum), tomatoes, cucumber, watermelon, squash, and pumpkin (29,35, 40,57,73). The disease was first described on bell pepper in New Mexico in 1922 (40). In recent years, epidemics have been severe in areas of North Carolina, Florida, Georgia, Michigan, and New Jersey. Oospores are believed to provide the initial source of inoculum in the field, and the disease is polycyclic within seasons (1,7,59,60,67). In this article, we discuss the biology and epidemiology of Phytophthora blight on bell pepper and also describe management strategies that can be implemented based on existing knowledge of the ecology of this devastating pathogen. The objectives of ecologically based pest management (EBPM) are the safe, profitable, and durable management of pests that includes a total systems approach (25). EBPM relies primarily on biological input of knowledge concerning a pathogen life cycle, and secondarily, when necessary, on physical, chemical, and biological supplements for disease management. An understanding of the ecological processes that are suppressive to plant diseases is emphasized rather than secondary inputs (25). Fortunately, we have a considerable amount of information available on the biology and ecology of P. capsici, which can now be integrated to improve our ability to manage the disease using ecologically based approaches. Strategies recommended for management of Phytophthora blight involve integrated approaches that focus first on cultural practices that reduce high soil moisture conditions, but also include monitoring and reduction of propagules of P. capsici that persist in the soil, utilization of cultivars with resistance to the disease, and when necessary, judicious fungicide applications. Symptoms and Life Cycle P. capsici can infect virtually every part of the pepper plant. The pathogen causes a root and crown rot on pepper (Fig. 1) and also forms distinctive black lesions on the stem (Fig. 2). P. capsici can also infect the leaves and causes lesions that are circular, grayish brown, and water-soaked (Fig. 3). Leaf lesions and stem lesions are common when inoculum is splash dispersed from the soil to lower portions of the plant. The pathogen can also infect fruit and causes lesions that are typically covered with white sporangia, a sign of the pathogen (Fig. 4). P. capsici typically causes a fruit rot or stem rot on cucumbers and squash (Fig. 5). P. capsici reproduces by both sexual and asexual means (Fig. 6). The pathogen produces two mating types, known as the A1 and A2. These are actually compatibility types and do not correspond to dimorphic forms. Each mating type produces hormones that are responsible for gametangia differentiation in the opposite mating type. Both A1 and A2 mating types are common in fields in North Carolina and have also been identified within the same plant (59). P. capsici produces a male gametangium, called the antheridium, and a female gametangium, called the oogonium. The antheridium is amphigynous in this species. Meiosis occurs within the gametangia, and plasmogamy and karyogamy result

Aegilops tauchii is a D-genome donor of hexaploid wheat and is a potential source of genes for various biotic and abiotic stresses including heat and drought. In the present study, we used multi-stage evaluation technique to understand the effects of heat and drought stresses on Ae. tauschii derived introgression lines (ILs). Preliminary evaluation (during stage-I) of 369 ILs for various agronomic traits identified 59 agronomically superior ILs. In the second stage (stage-II), selected ILs (i.e., 59 ILs) were evaluated for seedling heat (at 30°C and 35°C) and drought (at 20% poly-ethylene glycol; PEG) stress tolerance under growth chambers (stage-II). Heat and drought stress significantly reduced the seedling vigour by 59.29 and 60.37 percent, respectively. Genotype×treatment interaction analysis for seedling vigour stress tolerance index (STI) identified IL-50, IL-56, and IL-68 as high-performing ILs under heat stress and IL-42 and IL-44 as high-performing ILs under drought stress. It also revealed IL-44 and IL-50 as the stable ILs under heat and drought stresses. Furthermore, in the third stage (stage-III), selected ILs were evaluated for heat and drought stress tolerance under field condition over two cropping seasons (viz., 2020-21 and 2021-22), which significantly reduced the grain yield by 72.79 and 48.70 percent, respectively. Stability analysis was performed to identify IL-47, IL-51, and IL-259 as the most stable ILs in stage-III. Tolerant ILs with specific and wider adaptability identified in this study can serve as the potential resources to understand the genetic basis of heat and drought stress tolerance in wheat and they can also be utilized in developing high-yielding wheat cultivars with enhanced heat and drought stress tolerance.

The present research was taken out to assess the physiological, biochemical, and photosynthetic responses of the chickpea (Cicer arietinum L) to the combination of clay-bentonite and saline water in greenhouse conditions, at four concentrations of NaCl (0, 50, 100 and 200 mM). A substantial decrease in all the studied parameters (germination rate, root and stem length, fresh weight or dry weight, relative water content and chlorophyll content) was observed when salinity was increased. However, the application of various NaCl concentrations improved the total soluble protein and soluble sugar content in plants cultivated in the substrate without bentonite. The imposition of 50 mM NaCl with bentonite increased total soluble protein content. In contrast, the 100 and 200 mM treatment led to decreased total soluble protein content. The use of the bentonite did not produce any changes into depreciating of the effect of NaCl stress. On the other hand, salinity-bentonite exacerbated a reduction in physiological and biochemical processes of chickpea. Indeed, the K+/Na+ ratio decreased in all organs of plants with increasing NaCl doses. This ratio is slightly in favor of K+ only in substrate without bentonite. Our findings indicated that salinity-bentonite exacerbated a reduction in physiological and biochemical processes.

Salinity is considered as major environmental challenge that affects crop growth and productivity. This study investigated the application of Haodule univervis seagrass liquid extract on bell pepper (Capsicum annuum L.) under salt stress conditions. The salinity treatments were applied by irrigating bell pepper plants with 0, 50, 100, 150, and 200 mM/l of NaCl with four replications. The bell pepper plants were divided into two groups: one group was sprayed with seagrass extract, and the other group was sprayed with distilled water. The salt treatment was applied at every 10 days interval for only three treatments, and the bell pepper leaves were sprayed about seven days after the salt treatment. The results showed an increase in relative water content (RWC) of salt stressed bell pepper plants sprayed with seagrass extract from 0- 100 mM of NaCl treatment, while RWC decreased at 150 and 200 mM NaCl treatments compared to the control. This indicates stressed bell pepper plants sprayed with seagrass extract had higher RWC than plants sprayed with water at 0-100 mM NaCl treatments. Chlorophyll concentration was decreased dramatically in plants sprayed with water at 50mM of NaCl level. However, chlorophyll concentration increased slightly in plants sprayed with water at 100 mM NaCl level then start declined gradually at 150 mM and 200mM NaCl level. The plants sprayed with seagrass extract showed an increase in chlorophyll concentration at 100 and 150 mM NaCl treatment compared to the control. Fresh weights of plants sprayed with seagrass extract were declined at 50-150 mM NaCl compared to the control. However, the highest dry weights of plants sprayed with seagrass at 100 mM NaCl treatment. In addition, plants sprayed with water did not show variations in fresh and dry weights.

Salinity is one of the abiotic stresses that affect crop growth and productivity in arid and semi-arid regions. Unfortunately, there are few known methods to mitigate the deleterious impacts of salt stress on the development and yield of vegetable crops. Blue-green algae (cyanobacteria) are endowed with the potential to curb the negative impacts of salt stress as they are characterized by biostimulant properties. The present work aimed to investigate the effects of Roholtiella sp. as a foliar extract on the growth characteristics, physiological and biochemical responses of bell pepper (Capsicum annuum L.) plants under varying levels of salinity conditions. A soilless water experiment was carried out in a greenhouse where bell pepper seedlings were grown under five salt concentrations (0, 50, 200, 150, and 200 mM of NaCl). Growth characteristics, pigments content, relative water content, and antioxidant activity (CAT) were determined. Our results showed that growth parameters, relative water content (RWC), chlorophyll a & b concentrations under salinity conditions were negatively affected at the highest concentration (200 mM). Interestingly, the application of Roholtiella sp. foliar extract enhanced the plant growth characteristics as shoot length increased by 17.014%, fresh weight by 39.15%, dry and weight by 31.02%, at various salt treatments. Moreover, chlorophyll a and b increased significantly compared with seedlings sprayed with water. Similarly, RWC exhibited a significant increase (92.05%) compared with plants sprayed with water. In addition, antioxidants activities and accumulation of proline were improved in Roholtella sp. extract foliar sprayed seedlings compared to the plants foliar sprayed with water. Conclusively, at the expiration of our study, the Rohotiella sp. extract-treated plants were found to be more efficient in mitigating the deleterious effects caused by the salinity conditions which is an indication of an enhancement potential of tolerating salt-stressed plants when compared to the control group.

This study was conducted to investigate the effects of high temperatures on three tomato cultivars at first bloom and yield stages. The leaves were subjected to high temperature stress at 35, 40, 45, 50, 55 and 60°C with gradual increments every 30-minutes in both stages. Samples were analyzed for total chlorophyll (Chl), carotenoid (Car), ascorbic acid (AsA), glutathione (GSH), total soluble protein (TSP) contents. Besides, protein profiles were determined with SDS-PAGE. Heat stress decreased Chl content in both stages, while it was higher in first bloom stage than in yield stage. Whereas carotenoid content increased in both stages. The AsA and GSH contents were higher in yield stage than in first bloom stage. Heat stress, generally reduced AsA content, while increased GSH content. It was observed that the effect of cultivars and temperature treatments on the TSP content was different in both periods. In addition, TSP content had decreased with increasing temperatures, while many protein bands had been observed in SDS-PAGE with sizes ranging from 13 kDa to 89 kDa according to treatments.

A pot study was performed to evaluate the influence of methionine (0, 25 and 50 mg L-1) as foliar spray on maize (Zea mays L.) varieties named as DTC (hybrid) and Malika under salt (90 mM NaCl) stress. Seeds of both maize varieties were sown in plastic pots under completely randomized design. Two-week-old maize plants were subjected to two levels of salt stress i.e., 0 and 90 mM (NaCl) in full strength Hoagland’s nutrient solution. Foliar application of different methionine levels (0, 25 and 50 mg L-1) was applied to four-week-old maize plants. A three way analysis of variance (ANOVA) of data of 11-week-old plants of maize plants showed that salt stress considerably reduced the growth, chlorophyll, relative water content (%), free amino acids and flavonoid contents, whereas improved membrane permeability (%), total leaf area per plant, glycine betaine (GB), total soluble proteins, free proline, anthocyanin and ascorbic acid contents of both maize varieties. Maize var. Malka was greater in fresh weight of root, total chlorophyll and total soluble protein contents, while DTC (hybrid) excelled in anthocyanin, total soluble sugars and flavonoid contents. Methionine as foliar application significantly improved dry shoot weight, fresh root weight, GB, total soluble protein, ascorbic acid and anthocyanin contents of two maize varieties under salinity stress. Of the varying methionine levels, 50 mg L-1 proved better in decreasing the adverse influence of NaCl stress on both varieties [DTC (hybrid) and Malika] of maize. Key words: proteins, salinity, oxidative stress, vitamins, ascorbic acid

Crop reflectance indices for mapping water stress in greenhouse grown bell pepper

Previously, we isolated CDS of Ziziphus nummularia isoform ZnJClpB1-C from heat stress-tolerant genotype Jaisalmer. To further functionally validate ZnJClpB1-C assumed function in tobacco and to generate novel germplasm for heat stress tolerance, this gene was transformed in theNicotiana tabacum. ClpB proteins are the major key player required for basal and induced heat stress tolerance in plant cells under heat stress. In Ziziphus nummularia ClpB1-C transcript from genotype Jaisalmer was highly upregulated under heat stress conditions, as reported earlier. Nine transgenic lines (T1) from three transgenic tobacco events with single-copy integration (T0 stage) were taken for heat stress analysis at seedling stage. Mature tobacco transgenic plants did not show any deformity as compared to wild plants when grown under normal conditions. Overexpression of ZnJClpB1-C in tobacco significantly increased the tolerance to heat stress. Under heat stress conditions (42°C), T1 transgenic tobacco seedlings showed higher photosynthetic rate, relative water content, membrane stability index and lower levels of MDA, compared to the wild type untransformed plants. The qRT-PCR analysis revealed different level of transgene expression (1.08 to 3.89 folds) in 9 T1 transgenic lines. In vitro roles of ZnJClpB1-C regulating thermotolerance is not reported so far. These results demonstrated the positive roles of ZnJClpB1-C in enhancing thermotolerance and its use as a genomic resource in the near future for developing heat stress-tolerant germplasm.

Objective: To quantify the one-year total soluble protein (TSP) concentration in the trunk of two pine species.
 Design/Methodology/Approach: The Bradford method (1976) was used to determine the TSP concentration in the two pine species. Statistical tests were subsequently performed with the IBM SPSS 18 Software, using a general linear model (GLM) univariate analysis.
 Results: The TSP concentration was different for each month. The highest concentration was recorded in August (6.84 mg gMS-1 for Pinus pinceana Gordon and 6.82 mg gMS-1 for Pinus cembroides Zucc), and the lowest was registered in April (5.53 mg gMS-1 for Pinus cembroides Zucc) and February (6.64 mg gMS-1 for Pinus pincenana Gordon).
 Study Limitations/implications: There is a lack of information regarding these two pine species and scarce studies explain the behavior of the TSP.
 Conclusions: The concentration of total soluble proteins varies in each month of the year. Further studies that include more plant organs are required to obtain a broader protein profile for both species.

Heat stress is a serious threat to crop production due to increased ambient temperature in many regions of the world. Most crop plants are sensitive to heat stress that led to progressive decreasing in yields at temperatures above the optimum level. Projected increases in temperature will negatively affect yield production and threaten the food security. Key adaptive mechanisms in crops that grown under the effect of heat stress including; rapid growth and early maturity, vitality of the leaves, chlorophyll content, stomatal conductivity and the transpiration rate, relative water content, antioxidants, heat shock proteins and cell membrane thermostability. These plant traits may contribute to enhance stress tolerance of plants. Identification of heat resistance genes and the development of new cultivars, whether in breeding methods or genetic engineering, is an effective means of reducing the harmful effects of heat stress. So, follow agricultural procedures such as cultivate the tolerant cultivars and adjusted crop irrigation dates with meteorological data and proper fertigation programs are other options in reducing the effects of heat stress waves.