Proline Accumulation Research Articles

Incremento de la prolina por la aplicación del bioestimulante CBX-103 mejora el crecimiento de Arabidopsis thaliana Col 0 bajo condiciones de estrés salino

Agriculture faces new, increasingly complicated challenges in the face of a constantly changing environment that causes different types of stress in crops, one of them being salinity. Numerous investigations have been carried out to understand the effect of salt stress on the physiology of plants, as well as different ways of dealing with it and creating tolerance and/or resistance so that the productivity of crops is not affected. Among these alternatives we find biostimulants. The biostimulant CBX-103 is composed of carboxylic acids, succinic acids, oligogalacturonides, among others, which are obtained through a controlled enzymatic fermentation of the plant extract of Saccharum officinarum L. In the present study it is demonstrated that foliar applications of the biostimulant CBX- 103 in Arabidopsis thaliana Col 0 plants grown under salt stress increase leaf proline content, significantly reducing the harmful effects of stress, which is demonstrated at a biometric level and regulating growth states. A pathway in the energy regulation of plants is proposed as a mode of action due to the increase in the accumulation of proline obtained and the effect of its components.

Proline metabolism and its osmotic regulatory role in enhancing hypersalinity tolerance of the razor clam (Sinonovacula constricta)

Proline serves as an important osmolyte in maintaining osmotic pressure and stabilizing cellular structure in aquatic organisms, and is essential for adaptation to salinity stress. This study focuses on the razor clam (Sinonovacula constricta), and investigated the metabolism and synthesis of proline in response to changing salinity. The proline content in gill tissues of razor clams significantly increased over time and with different levels of salinity exposure. The key genes involved in proline metabolism, including (Aminotransferase (ScOAT), Δ1-pyrroline-5-carboxylic acid synthase (ScP5CS), and proline dehydrogenase (ScProDH) were investigated, as well as enzyme activities associated with these genes in razor clams. The expression and activity of P5CS increased significantly under hypersalinity conditions, whereas that of OAT enzyme activity decreased. This suggested that the glutamate pathway had an important role in the proline synthesis during hypersalinity. ProDH activity was negatively correlated with salinity and regulated by the proline content, indicating a significant role of ProDH in proline accumulation under hypersalinity conditions. ScP5CS was heterologously expressed in yeast Saccharomyces cerevisiae, followed by exogenous proline supplementation studies. Recombinant S. cerevisiae incubated with ScP5CS exhibited elevated levels of proline, with the growth performance of recombinant strain surpassing that of the control group after salinity stress. In addition, razor clams exposed to exogenous proline under high salinity conditions showed expedite osmotic regulation, whereby the hemolymph pressure reached equilibrium more quickly. Together, these results indicated that the proline content increased under high salinity, which could improve the tolerance of razor clams to hypersalinity, offering novel perspectives into molecular mechanism of salinity adaptation in shellfish.

Effect of biopriming and nanopriming on physio-biochemical characteristics of Cicer arietinum L. under drought stress

Drought, a detrimental abiotic stress, disturbs many vital processes critical to plant growth and development resulting in subpar crop yield. Unconventional measures such as biofertilizers and nanofertilizers have been reported as reliable solutions to this, however, outcomes vary greatly depending upon the type of organism/particle and its mode of delivery. Seed priming involves treating seeds with organic/inorganic chemicals to ameliorate drought stress by boosting pre-germinative metabolism, maintaining water potential, scavenging free radicals, etc. Therefore, this study determined the effect of biopriming and nanopriming on germination percentage (GP), leaf water status (LWS), proline, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and survial percentage (SP) of BG-4958 (Drought tolerant) and ICC-1882 (Drought sensitive) chickpea varieties exposed to polyethylene glycol (PEG) induced moderate (5 %) and severe drought (10 %) at flowering with no drought acting as a control. Experimental setup had three groups, control (untreated), bioprimed with plant growth promoting endophytic bacteria (PGPEB), and nanoprimed with CuNPs synthesised from PGPEB and their chemical counterparts). Crop analysis after 15 DDS (Days to drought stress) revealed that priming significantly altered the physio-biochemical parameters. Consortium and N2X led highest increment in GP and SP for DT and DS varieties, respectively, whereas N1X showed highest increase in LWS of both. Highest accumulation of proline was observed with consortium and N1 (X & Y) in DS variety while only biological CuNPs accumulated proline for DT variety. MDA and H₂O₂ decreased significantly in treated groups thereby reducing oxidative damage with non-significant variations in DT. Lower concentrations of biological CuNPs were found to be more effective in modulating the physio-biochemical machinery of chickpea under drought than their higher concentration as well as chemical counterparts. This study deepens our understanding of the beneficial role of PGPEB and biosynthesized CuNPs in alleviating the adverse effects of drought in chickpea.

Endophytic Bacillus pumilus G5 Interacting with Silicon to Improve Drought Stress Resilience in Glycyrrhiza uralensis Fisch. by Modulating Nitrogen Absorption, Assimilation, and Metabolism Pathways.

Drought stress has become the primary severe threat to global agriculture production, including medicinal plants. Plant growth-promoting bacteria (PGPB) and environmentally friendly element silicon (Si) have emerged as effective methods in alleviating drought stress in various plants. Here, the effects of the plant endophytic G5 interaction with Si on regulating nitrogen absorption, assimilation, and metabolism pathways were investigated in the morphophysiological and gene attributes of Glycyrrhiza uralensis exposed to drought. Results showed that G5+Si application improved nitrogen absorption and assimilation by increasing the available nitrogen content in the soil, further improving the nitrogen utilization efficiency. Then, G5+Si triggered the accumulation of the major adjustment substances proline, γ-aminobutyric acid, putrescine, and chlorophyll, which played an important role in contributing to maintaining balance and energy supply in G. uralensis exposed to drought. These findings will provide new ideas for the combined application of PGPR and Si on both soil and plant systems in a drought habitat.

Adoption of arbuscular mycorrhizal fungi and biochar for alleviating the agro-physiological response of lavander (Lavandula angustifolia L.) subjected to drought stress

Increasing the productivity of crops in water deficit circumstances is of great significance in order to face the challenge of securing global food production. Nowadays, the use of biochar (BC) and arbuscular mycorrhizal fungi (AMF) are considered as one of the most effective methods for empowering plants to deal with drought stress. However, the literature regarding the effects of the simultaneous use of AMF+BC on plants under drought stress is scarce. Hence, the present study was conducted to consider the combined application of AMF and biochar on the physiological and biochemical properties of lavender under various levels of irrigation. The first factor includes three irrigation regimes of 90 % field capacity (FC), 60 % FC, and 30 % FC, respectively, corresponding to normal irrigation, mild and severe drought stress. The second factor included a fertilizer or microbial inoculant source, which were respectively: no inoculation (control), inoculation with AMF, BC, and co-application of AMF along with BC. The highest nutrient, chlorophyll and carotenoid content, and fresh, and dry weight of lavender were recorded under normal irrigation conditions with combined application of AMF+BC. The combined application of AMF+BC was significantly effective in increasing the activity of antioxidant enzymes against oxidative damage caused by drought stress and in reducing the accumulation of proline and malondialdehyde. An increase in phenolic, flavonoid, and concentration of essential oil was observed under mild stress and using AMF+BC, while the highest essential oil yield was recorded under a normal irrigation regime and treated with AMF+BC. The highest content of linalool, camphor, borneol, and linalyl acetate was obtained in mild stress by adding AMF+BC. It can be concluded that the use of AMF+BC combination treatment may be a useful strategy to improve the quantity and quality of lavender EO in drought-stress circumstances.

Response strategies of slash pine (Pinus elliottii) to cadmium stress and the gain effects of inoculation with Herbaspirillum sp. YTG72 in alleviating phytotoxicity and enhancing accumulation of cadmium.

Phytoremediation using fast-growing woody plants assisted by plant growth-promoting bacteria (PGPB) on cadmium (Cd)-contaminated sites is considered a promising technique; however, its remediation efficiency is still affected by multiple factors. In this study, the mining areas' soil conditions were simulated with different Cd addition levels (0, 3, 6, 9mgkg-1) in order to investigate the response strategy to Cd stress of fast-growing economic tree species, slash pine (Pinus elliottii), and the effects of inoculation with the PGPB strain Herbaspirillum sp. YTG72 on the physiological activity and Cd accumulation of plants. The main results showed that there were significant (p < 0.05) increases in contents of chlorophyll and nutrient elements (P, K, Ca, and Mg) at low Cd addition level (3mgkg-1) compared to non-Cd addition treatment. When the additive amount of Cd increased, the growth of plants was severely inhibited and the content of proline was increased, as well as Cd in plants. Besides, the ratios of K:P, Ca:P, and Mg:P in plants were negatively correlated with the contents of Cd in plants and soils. Inoculation of P. elliottii with the PGPB strain Herbaspirillum sp. YTG72 improved the physiological functions of the plants under Cd stress and activated the antioxidant system, reduced the accumulation of proline, and decreased the ratios of K:P, Ca:P, and Mg:P in plant. More importantly, planting P. elliottii in Cd-contaminated soil could significantly (p < 0.05) reduce the Cd content in the rhizosphere soil, and furthermore, inoculation treatment could promote the reduction of soil Cd content and increased the accumulation of Cd by root. The results of the present study emphasized the Cd response mechanism of P. elliottii based on multifaceted regulation, as well as the feasibility of strain Herbaspirillum sp. YTG72 assisted P. elliottii for the remediation on Cd-contaminated sites.

Exogenous Application of Gamma Aminobutyric Acid Improves the Morpho-Physiological and Biochemical Attributes in Lavandula dentata L. under Salinity Stress

Saline water has been proposed as a solution to partially supply plants with their water requirements due to a lack of fresh water for cultivation in arid and semi-arid sites. Gamma-aminobutyric acid (GABA) is a non-protein amino acid participating in numerous metabolic processes to mitigate the undesirable effects of salinity. A pot experiment was carried out during 2021 and 2022 at Sakha Horticulture Research Station to investigate the effect of foliar application of GABA at 20 and 40 mM on vegetative growth and biochemical changes in French lavender under increasing levels of sea water salinity irrigation treatments (0, 1000, 2000, and 3000 ppm). Results indicated that increasing salinity concentration noticeably decreased plant height, number of branches, herb fresh and dry weight, root length, root fresh and dry weights, photosynthetic pigments, relative water content, and essential oil percentage. On the other hand, accumulation of proline and antioxidant enzymes was increased under increasing salinity concentrations. We conclude that foliar application of GABA acid at 40 mM can alleviate the adverse effects of salinity on the abovementioned French lavender plant characteristics by improving vegetative growth and root characteristics, as well as diminishing chlorophyll degradation, maintaining high leaf relative water content, increasing proline accumulation and antioxidant activity.

A calmodulin-like protein PvCML9 negatively regulates salt tolerance

Calmodulin-like proteins (CMLs) are unique Ca2+ sensors and play crucial roles in response to abiotic stress in plants. A salt-repressed PvCML9 from halophyte seashore paspalum (Paspalum vaginatum O. Swartz) was identified. PvCML9 was localized in the cytoplasm and nucleus and highly expressed in roots and stems. Overexpression of PvCML9 led to reduced salt tolerance in rice and seashore paspalum, whereas downregulating expression of PvCML9 showed increased salt tolerance in seashore paspalum as compared with the wild type (WT), indicating that PvCML9 regulated salt tolerance negatively. Na+ and K+ homeostasis was altered by PvCML9 expression. Lower level of Na+/K+ ratio in roots and shoots was maintained in PvCML9-RNAi lines compared with WT under salt stress, but higher level in overexpression lines. Moreover, higher levels of SOD and CAT activities and proline accumulation were observed in PvCML9-RNAi lines compared with WT under salt stress, but lower levels in overexpression lines, which altered ROS homeostasis. Based on the above data, mutation of its homolog gene OsCML9 in rice by CRISPR/Cas9 was performed. The mutant had enhanced salt tolerance without affecting rice growth and development, suggesting that OsCML9 gene is an ideal target gene to generate salt tolerant cultivars by genome editing in the future.

Genome-wide identification of the CNGC gene family and negative regulation of drought tolerance by HvCNGC3 and HvCNGC16 in transgenic Arabidopsis thaliana

Cyclic nucleotide-gated ion channels (CNGCs), as non-selective cation channels, play essential roles in plant growth and stress responses. However, they have not been identified in Qingke (Hordeum vulgare L.). Here, we performed a comprehensive genome-wide identification and function analysis of the HvCNGC gene family to determine its role in drought tolerance. Phylogenetic analysis showed that 27 HvCNGC genes were divided into four groups and unevenly located on seven chromosomes. Transcription analysis revealed that two closely related members of HvCNGC3 and HvCNGC16 were highly induced and the expression of both genes were distinctly different in two extremely drought-tolerant materials. Transient expression revealed that the HvCNGC3 and HvCNGC16 proteins both localized to the plasma membrane and karyotheca. Overexpression of HvCNGC3 and HvCNGC16 in Arabidopsis thaliana led to impaired seed germination and seedling drought tolerance, which was accompanied by higher hydrogen peroxide (H2O2), malondialdehyde (MDA), proline accumulation and increased cell damage. In addition, HvCNGC3 and HvCNGC16-overexpression lines reduced ABA sensitivity, as well as lower expression levels of some ABA biosynthesis and stress-related gene in transgenic lines. Furthermore, Yeast two hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays revealed that HvCNGC3 and HvCNGC16 interacted with calmodulin/calmodulin-like proteins (CaM/CML), which, as calcium sensors, participate in the perception and decoding of intracellular calcium signaling. Thus, this study provides information on the CNGC gene family and provides insight into the function and potential regulatory mechanism of HvCNGC3 and HvCNGC16 in drought tolerance in Qingke.

Unraveling the effect of phenolic extract derived from olive mill solid wastes on agro-physiological and biochemical traits of pomegranate and its associated rhizospheric soil properties

Agricultural waste management poses a significant challenge in circular economy strategies. Olive mill wastes (OMW) contain valuable biomolecules, especially phenolic compounds, with significant agricultural potential. Our study evaluate the effects of phenolic extract (PE) derived from olive mill solid wastes (OMSW) on pomegranate agro-physiological and biochemical responses, as well as soil-related attributes. Pomegranate plants were treated with PE at doses of 100 ppm and 200 ppm via foliar spray (L100 and L200) and soil application (S100 and S200). Results showed increased biomass with PE treatments, especially with soil application (S100 and S200). Proline and soluble sugar accumulation in leaves suggested plant adaptation to PE with low-level stress. Additionally, PE application reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents. Higher doses of PE (S200) significantly improved net photosynthesis (Pn), transpiration rate (E), water use efficiency (WUEi), and photosynthetic efficiency (fv/fm and PIabs). Furthermore, PE treatments enhanced levels of chlorophylls, carotenoids, polyphenols, flavonoids, and antioxidant activity. Soil application of PE also increased soil enzyme activities and microbial population. Our findings suggest the beneficial impact of PE application on pomegranate agro-physiological responses, laying the groundwork for further research across various plant species and soil types to introduce nutrient-enriched PE as an eco-friendly biostimulant.

Birch WRKY transcription factor, BpWRKY32, confers salt tolerance by mediating stomatal closing, proline accumulation, and reactive oxygen species scavenging

Plant WRKY transcription factors (TFs) play important roles in abiotic stress responses. However, how WRKY facilitate physiological changes to confer salt tolerance still needs to be studied. Here, we identified a WRKY TF from birch (Betula platyphylla Suk), BpWRKY32, which is significantly (P < 0.05) induced by salt stress. BpWRKY32 binds to W-box motif and is located in the nucleus. Under salt stress conditions, fresh weights (FW) of OE lines (BpWRKY32 overexpression lines) are increased by 66.36% than that of WT, while FW of knockout of BpWRKY32 (bpwrky32) lines are reduced by 39.49% compared with WT. BpWRKY32 regulates the expression of BpRHC1, BpNRT1, and BpMYB61 to reduce stomatal, and width-length ratio of the stomatal aperture in OE lines are reduced by 46.23% and 64.72% compared with in WT and bpwrky32 lines. BpWRKY32 induces P5CS expression, but inhibits P5CDH expression, leading to the proline content in OE lines are increased by 33.41% and 97.58% compared with WT and bpwrky32 lines. Additionally, BpWRKY32 regulates genes encoding SOD and POD family members, which correspondingly increases the activities of SOD and POD. These results suggested that BpWRKY32 regulates target genes to reduce the water loss rate, enhance the osmotic potential, and reduce the ROS accumulation, leading to improved salt tolerance.

Proline accumulation and antioxidant response are crucial for citrus tolerance to UV-B light-induced stress.

Plants face a wide range of biotic and abiotic stress conditions, which are further intensified by climate change. Among these stressors, increased irradiation in terms of intensity and wavelength range can lead to detrimental effects, such as chlorophyll degradation, destruction of the PSII reaction center, generation of ROS, alterations to plant metabolism, and even plant death. Here, we investigated the responses of two citrus genotypes, Citrus macrophylla (CM), and Troyer citrange (TC) to UV-B light-induced stress, by growing plants of both genotypes under control and UV-B stress conditions for 5 days to evaluate their tolerance mechanisms. TC seedlings had higher sensitivity to UV-B light than CM seedlings, as they showed more damage and increased levels of oxidative harm (indicated by the accumulation of MDA). In contrast, CM seedlings exhibited specific adaptive mechanisms, including accumulation of higher levels of proline under stressful conditions, and enhanced antioxidant capacity, as evidenced by increased ascorbate peroxidase activity and upregulation of the CsAPX2 gene. Phytohormone accumulation patterns were similar in both genotypes, with a decrease in ABA content in response to UV-B light. Furthermore, expression of genes involved in light perception and response was specifically affected in the tolerant CM seedlings, which exhibited higher expression of CsHYH/CsHY5 and CsRUP1-2 genes. These findings underscore the importance of the antioxidant system in citrus plants subjected to UV-B light-induced stress and suggest that CsHYH/CsHY5 and CsRUP1-2 could be considered genes associated with tolerance to such challenging conditions.

Synergistic effects of biochar and potassium co-application on growth, physiological attributes, and antioxidant defense mechanisms of wheat under water deficit conditions

Global wheat production faces a severe threat from drought stress, necessitating innovative strategies for enhanced crop resilience. This study examined the synergistic impact of biochar and potassium co-application on the growth, physiological attributes, and antioxidant defense system of wheat under water deficit conditions at crown root initiation (CRI), anthesis, and grain development stage. Drought-induced reactive oxygen species (ROS) accumulation, particularly pronounced at the CRI stage, adversely affected all growth stages. At CRI, co-application of biochar and foliar potassium delivered significant improvements in growth parameters, including increased plant height (15.4%), spike length (50%), grain yield (43.0%), photosynthetic performance (chlorophyll content 125.8%), and relative water content (11.2%), compared to untreated drought-exposed counterparts. The combined application of biochar and potassium effectively reduced hydrogen peroxide production, electrolyte leakage, proline accumulation, and malondialdehyde generation, while increasing relative water content and glutathione levels under both well-irrigated and drought stress conditions. Furthermore, the combined biochar and potassium treatment was effective in mitigating oxidative stress and enhancing physiological resilience in wheat, particularly during the anthesis stage of drought stress. Specifically, the combined treatment ameliorated the effects of drought by reducing ROS levels through enhanced antioxidant enzyme activities and elevating osmoprotectants levels. The synergistic modulation of tissue osmotic balance and relative water content holds promise for mitigating drought-induced stress, offering an innovative and practical strategy for resilient wheat production in water-limited environments.

Temporal Changes in Biochemical Responses to Salt Stress in Three Salicornia Species.

Halophytes adapt to salinity using different biochemical response mechanisms. Temporal measurements of biochemical parameters over a period of exposure to salinity may clarify the patterns and kinetics of stress responses in halophytes. This study aimed to evaluate short-term temporal changes in shoot biomass and several biochemical variables, including the contents of photosynthetic pigments, ions (Na+, K+, Ca2+, and Mg2+), osmolytes (proline and glycine betaine), oxidative stress markers (H2O2 and malondialdehyde), and antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) activities of three halophytic Salicornia species (S. persica, S. europaea, and S. bigelovii) in response to non-saline, moderate (300 mM NaCl), and high (500 mM NaCl) salinity treatments at three sampling times. Salicornia plants showed maximum shoot biomass under moderate salinity conditions. The results indicated that high Na+ accumulation in the shoots, coupled with the relative retention of K+ and Ca2+ under salt stress conditions, contributed significantly to ionic and osmotic balance and salinity tolerance in the tested Salicornia species. Glycine betaine accumulation, both constitutive and salt-induced, also seems to play a crucial role in osmotic adjustment in Salicornia plants subjected to salinity treatments. Salicornia species possess an efficient antioxidant enzyme system that largely relies on the ascorbate peroxidase and peroxidase activities to partly counteract salt-induced oxidative stress. The results also revealed that S. persica exhibited higher salinity tolerance than S. europaea and S. bigelovii, as shown by better plant growth under moderate and high salinity. This higher tolerance was associated with higher peroxidase activities and increased glycine betaine and proline accumulation in S. persica. Taking all the data together, this study allowed the identification of the biochemical mechanisms contributing significantly to salinity tolerance of Salicornia through the maintenance of ion and osmotic homeostasis and protection against oxidative stress.

Effects of microbial biofertilizer on growth, physio-biochemical traits, fruit yield, and water productivity of okra under drought stress

Drought poses a major challenge to global agricultural crop production, as it is considered one of the most severe abiotic stresses. Understanding the effects of exogenous microbial biofertilizer on okra [Abelmoschus esculentus (L.) Moench] under drought stress can lead to new strategies for coping with drought conditions. The objective of the study was to examine the effects of microbial biofertilizer on growth, physio-biochemical traits, fruit yield, and water productivity of okra under drought stress. A factorial pot experiment, consisting of eight biofertilizer treatments applied as a soil drench (autoclaved inoculum [control], and inoculation with arbuscular mycorrhizal fungi [AMF], phosphate-solubilizing fungi [PSF], plant growth-promoting rhizobacteria [PGPR], AMF + PSF, AMF + PGPR, PGPR + PSF, and AMF + PSF + PGPR) and three soil moisture regimes (50%, 75%, and 100% field capacity [FC]), was carried out. The results indicated that decreasing soil moisture level severely affected growth and fruit yield of okra. The application of microbial biofertilizer effectively enhanced growth, fruit yield, and physio-biochemical traits of okra under different soil moisture levels. Among the biofertilizer treatments considered, the combined application of AMF and PGPR showed remarkable efficacy in enhancing growth and productivity of okra plants under both 75% and 100% FC conditions. This co-inoculation significantly boosted shoot dry matter by 51%, root dry matter by 73%, fruit yield by 113%, and irrigation water productivity by 122% compared with plants grown without inoculation, irrespective of soil moisture levels. Furthermore, the plants treated with AMF and PGPR exhibited a noteworthy decrease in free proline accumulation by 31% compared with their non-inoculated counterparts. The results suggest that application of both AMF and PGPR biofertilizer to soil is an effective strategy to alleviate moderate drought stress. It is recommended to apply AMF and PGPR in combination to improve okra yield and water productivity under drought stress.

Near-Freezing Temperature Storage Improves Peach Fruit Chilling Tolerance by Regulating the Antioxidant and Proline Metabolism

Chilling injury (CI) in peach fruit (Prunus persica cv. Yuhualu) is generally caused by long-time low temperature (5 °C or 0 °C) storage. However, peach fruit stored at near-freezing temperature (NFT in this research is −1 °C), defined as within 0.5 °C above the biological freezing point of biological tissue, does not exhibit CI symptoms. The effect of NFT on the CI, proline metabolism, and antioxidant capability of peach fruit during storage was studied and compared with 5 °C and 0 °C storage as controls. The results exhibit that NFT completely inhibited the occurrence of CI in peach fruit. NFT significantly (p &lt; 0.05) enhanced the activities of superoxide dismutase, catalase, ascorbate peroxidase, and 1,1-diphenyl-2-picrylhydrazyl scavenging capacity. Moreover, the increase of malondialdehyde, ion leakage, and H2O2 accumulation were inhibited remarkably by NFT, and decreases in the contents of phenolics and ascorbic acid were slowed significantly in peach fruit stored at NFT (p &lt; 0.05). Additionally, NFT storage enhanced proline accumulation by modulating the activity of proline metabolizing enzymes. In conclusion, the above results suggest that NFT storage can improve the chilling tolerance of peach fruit by regulating the antioxidant defense and proline metabolism, which might represent a potential novel method to store fruits and vegetables for longer storage times.

Low Nitrogen Input Mitigates Quantitative but Not Qualitative Reconfiguration of Leaf Primary Metabolism in Brassica napus L. Subjected to Drought and Rehydration.

In the context of climate change and the reduction of mineral nitrogen (N) inputs applied to the field, winter oilseed rape (WOSR) will have to cope with low-N conditions combined with water limitation periods. Since these stresses can significantly reduce seed yield and seed quality, maintaining WOSR productivity under a wide range of growth conditions represents a major goal for crop improvement. N metabolism plays a pivotal role during the metabolic acclimation to drought in Brassica species by supporting the accumulation of osmoprotective compounds and the source-to-sink remobilization of nutrients. Thus, N deficiency could have detrimental effects on the acclimation of WOSR to drought. Here, we took advantage of a previously established experiment to evaluate the metabolic acclimation of WOSR during 14 days of drought, followed by 8 days of rehydration under high- or low-N fertilization regimes. For this purpose, we selected three leaf ranks exhibiting contrasted sink/source status to perform absolute quantification of plant central metabolites. Besides the well-described accumulation of proline, we observed contrasted accumulations of some "respiratory" amino acids (branched-chain amino acids, lysineand tyrosine) in response to drought under high- and low-N conditions. Drought also induced an increase in sucrose content in sink leaves combined with a decrease in source leaves. N deficiency strongly decreased the levels of major amino acids and subsequently the metabolic response to drought. The drought-rehydration sequence identified proline, phenylalanine, and tryptophan as valuable metabolic indicators of WOSR water status for sink leaves. The results were discussed with respect to the metabolic origin of sucrose and some amino acids in sink leaves and the impact of drought on source-to-sink remobilization processes depending on N nutrition status. Overall, this study identified major metabolic signatures reflecting a similar response of oilseed rape to drought under low- and high-N conditions.

Exogenous strigolactone enhanced the drought tolerance of pepper (Capsicum chinense) by mitigating oxidative damage and altering the antioxidant mechanism.

Exogenous SL positively regulates pepper DS by altering the root morphology, photosynthetic character, antioxidant enzyme activity, stomatal behavior, and SL-related gene expression. Drought stress (DS) has always been a problem for the growth and development of crops, causing significant negative impacts on crop productivity. Strigolactone (SL) is a newly discovered class of plant hormones that are involved in plants' growth and development and environmental stresses. However, the role of SL in response to DS in pepper remains unknown. DS considerably hindered photosynthetic pigments content, damaged root architecture system, and altered antioxidant machinery. In contrast, SL application significantly restored pigment concentration modified root architecture system, and increased relative chlorophyll content (SPAD). Additionally, SL treatment reduced oxidative damage by reducing hydrogen peroxide (H2O2) (24-57%) and malondialdehyde (MDA) (79-89%) accumulation in pepper seedlings. SL-pretreated pepper seedlings showed significant improvement in antioxidant enzyme activity, proline accumulation, and soluble sugar content. Furthermore, SL-related genes (CcSMAX2, CcSMXL6, and CcSMXL3) were down-regulated under DS. These findings suggest that the foliar application of SL can alleviate the adverse effects of drought tolerance by up-regulating chlorophyll content and activating antioxidant defense mechanisms.

Assessing the air salinity on agro-physiological response of Brassica oleracea var. capitata and Brassica oleracea var. botrytis

Air salinity is one of the problems for horticulture production in coastal areas. Cabbage and Cauliflower are horticulture commodities that have the potential to develop in coastal areas. The present study aimed to examine the agro-physiological response of cabbage (Brassica oleracea var. capitata) and cauliflower (B. oleracea var. botrytis) to different concentrations of air salinity. This research was a factorial experiment on polybags arranged according to a completely randomized block design with two factors. The first factor was the crop type, namely cabbage (Grand 22) and cauliflower (Larissa F1). The second factor was the concentration of air salinity, namely 0 dS. m-1, 6 dS. m-1, 12 dS. m-1, and 18 dS. m-1. The agro-physiological changes studied were crop yield, leaf chlorophyll content, stomata density, and proline content. A stress tolerance index was measured to determine the level of crop resistance to air salinity stress. The results explained that air salinity was not able to affect crop growth and yield, but it enabled to affect crops physiologically. The highest decrease in leaf chlorophyll content was at 18 dS. m-1 of 29.16% in the vegetative stage and 37.88% in the generative stage. There was an increase in proline accumulation of leaf (1,320.63%) when the air salinity was increased (18 dS. m-1). However, the accumulation of cabbage proline was lower than that of cauliflower. Based on the stress tolerance index, cabbage is included in the category of tolerant, while cauliflower is in the category of moderate tolerance to air salinity.

Citrus rootstocks vs. nematodes: A battle for resistance against Tylenchulus semipenetrans

Tylenchulus semipenetrans, the causal agent of the ‘citrus slow decline’, is considered to be the most devastating nematode pest of citrus, causing considerable crop losses throughout the world. The management of this citrus nematode represents a significant challenge due to its wide host range and its adaptability to various environmental conditions. Nematicides application is the most prevalent control approach, however, their use often is associated with increased production costs and major risks to consumer health and the environment. The objective of this study is to contribute to the development of an alternative and effective method to control this plant-parasite. It intends to evaluate the resistance of the seven commonly used citrus rootstocks in Morocco based on their agronomic, physiological, and biochemical behavior in response to inoculation with T. semipenetrans. Results indicated that T. semipenetrans exhibited a strong reproductive capacity on Sour Orange, Australian sour orange, and volkameriana, showing higher root and soil infestation rates, with respectively 466.3, 250.5, and 273.3 females/10 g of root, and 1062.2, 1030.7, and 1053.2 females per 100 g of soil, compared to the other rootstocks varieties. These rootstocks allowed highest T. semipenetrans reproduction rates in both rhizospheric soil (> 3) and root (> 0.68), they also showed the highest infestation rate with more than 3 nematodes per cm of root. Moreover, these rootstocks showed significant biochemical alterations including a sharp increase in the activity of antioxidant enzymes, catalase (CAT), peroxidase (PO), polyphenol-oxidase (PPO), and in proline and malondialdehyde (MDA) accumulation compared to the control and other tested rootstocks. In contrast, T. semipenetrans reproduced poorly (with less than 135 females/10 g of root), less infested the roots (less than 0.33 females/cm of root), and induced slight biochemical modifications in Carrizo citrange. Thus, Carrizo citrange endowed with high resistance to T. semipenetrans could serve as a suitable rootstock to control this citrus devastating nematode.