Photosynthesis, ionomics and metabolomics of the host-hemiparasite association Acacia gerrardii-Viscum schimperi.

Viscum schimperi is an evergreen hemiparasitic plant that can grow on stems and branches of several tree species. It penetrates the host tissues and forms a vascular bridge (haustorium) to withdraw the nutritive resources. Its relationships with hosts remain unknown. This study aimed to investigate the physiological and biochemical attributes of the host-hemiparasite association Acacia gerrardii -Viscum schimperi . The hemiparasite exhibited 2.4- and 3.0-fold lower photosynthetic activity and water use efficiency, and 1.2- and 4.1-fold higher transpiration rate and stomatal conductance. Equally, it displayed 4.9- and 2.6-fold greater water potential and osmotic potential, and in least 3.0times more accumulated 39 K, 85 Rb and 51 V, compared to the host. Nevertheless, it had no detrimental effect on photosynthetic activity, water status and multi-element accumulations in the host. Based on metabolome profiling, V. schimperi could use xanthurenic acid and propylparaben to acquire potassium from the host, and N -1-naphthylacetamide and N -Boc-hydroxylamine to weaken or kill the distal part of the infected branch and to receive the total xylem contents. In contrast, A. gerrardii could used N -acetylserotonin, arecoline, acetophenone and 6-methoxymellein to defend against V. schimperi infection.

Physiological and biochemical attributes of the association host-parasite Tamarix aphylla-Plicosepalus acacia.

Parasitic plants have been viewed as pests since they are able to damage agricultural crops and forest trees. They establish vasculature connections with the hosts and withdraw the required nutritive resources. This study aimed to explore the physiological and biochemical effects of the parasitic plant Plicosepalus acacia on the host Tamarix aphylla. It was conducted on young fully expanded leaves from the uninfected and infected trees and the parasitic plant 'in situ'. The parasite had higher net photosynthetic assimilation rate (A), transpiration rate (E) and stomatal conductance (gs) compared to the host. Equally, it had two-fold greater water potential (Ψ) and osmotic potential (Ψs). It accumulated high amount of K, while it avoided accumulation of the most trace and ultratrace elements. Otherwise, parasitism seemed to increase A, WUE, water uptake and accumulation of the most major, trace and ultra-trace elements, however it reduced the accumulation of osmolytes at the infected plants. Based on UPLC-MS approach, P. acacia seemed to use a group of composites to interact with the host, including oleamide as a protector metabolite against host's defense system, carvone to establish vasculature connections with the host, cuminaldehyde to weaken growth and proliferation of the host, and caprolactam to weaken the distal part of the host. In contrast, the host T. aphylla could be used pipecolinic acid and nicotinamide to regulate systemic resistance and to defense against the parasite infection. Finally, despite the defense molecular interactions between the two partners, the parasitic plant exhibited several beneficial effects on the host.

Anticancer, anti-proliferative activity of Avicennia marina plant extracts.

PURPOSE: Medical halophytes plants are potent sources of bioactive secondary metabolite components used against different diseases. Avicenniamarina one of the typical halophytes plant species used in folk medicine to treat smallpox, rheumatism, and ulcer. Despite the richness of A.marina with polyphenolic, flavonoids, terpenoid, and terpene, contents remain poorly investigated against cancer types. Consequently, to explore the function-composition relationship of A.marina hexane leaves crude extract, the current study designed to investigate the cytotoxicity, apoptotic and antiproliferative impacts on the colon (HCT-116), liver (HepG2), and breast (MCF-7) cancer cell lines. MATERIALS AND METHODS: Therefore, the cytotoxicity impact screening carried out by Sulforhodamine-B assay. While, the initiation of the apoptosis evaluated by chromatin condensing, early apoptosis, late apoptosis and the formation and appearance of apoptotic bodies. On the other hand, the flow cytometry used to identify the phase of inhibition where the determined IC50 value used. While, the chemical composition of the hexane extract was detected using liquid chromatography-mass spectrometry/mass spectrometry. RESULTS: Revealed that hexane extract showed a weak induction of apoptosis despite the formation of apoptotic bodies and the high cell inhibitory effect on all tested cell lines with IC50 values (23.7 ± 0.7, 44.9 ± 0.93, 79.55 ± 0.57) µg/ml on HCT-116, HepG2, and MCF-7, respectively. Furthermore, it showed the ability to inhibit cell cycle in G0/G1 for HCT-116, S phase for HepG2, and MCF-7. CONCLUSION: In the light of these results, the current study suggests that A.marina leaves hexane extract may be considered as a candidate for further anticancer drug development investigations.

Interactive effects of salinity and iron deficiency in Medicago ciliaris.

In calcareous salt-affected soils, iron availability to plants is subjected to the effects of both sodium and bicarbonate ions. Our aim was to study interactive effects of salinity and iron deficiency on iron acquisition and root acidification induced by iron deficiency in Medicago ciliaris L., a species commonly found in saline ecosystems. Four treatments were used: C, control treatment, complete medium (CM) containing 30 microM Fe; S, salt treatment, CM with 75 mM NaCl; D, deficient treatment, CM containing only 1 microM Fe; DS, interactive treatment, CM containing 1 microM Fe with 75 mM NaCl. Our study showed that plant growth and chlorophyll content were much more affected by the interactive treatment than by iron deficiency or by the salt treatment, indicating an additive effect of these constraints in DS plants. These results could be partially explained by Na accumulation in shoots as well as a limitation of nutrient uptake such as Fe and K under salt stress, under iron deficiency, and especially under their combined effect. The study also showed that root acidification was deeply diminished when iron deficiency was associated with salinity. This probably explained the decrease of Fe uptake and suggested that root proton pump activity would be inhibited by salinity.

Contribution of NaCl excretion to salt resistance of Aeluropus littoralis (Willd) Parl.

Aeluropus littoralis is a perennial halophyte, native to coastal zones. Although it is usually exposed to high saline, this plant grows normally without toxicity symptoms. In order to assess leaf salt excretion, different growth parameters, Na(+), K(+), Ca(2+), Mg(2+) and Cl(-) concentrations, as well as excreted ions were examined in plants grown for 2 months in the presence of various salinity levels (0-800 mM NaCl). In addition, salt crystals, salt glands and other leaf epidermal structures were investigated. Results showed that total plant growth decreased linearly with increase to medium salinity. This reduction concerns mainly shoot growth. In addition, this species was able to maintain its shoot water content at nearly 50% of the control even when subjected to 800 mM NaCl. Root water content seemed to be unaffected by salt. Sodium and chloride ion contents in shoots and in roots increased with salinity concentrations, in contrast to our observation for potassium. However, calcium and magnesium contents were not greatly affected by salinity. Excreted salts in A. littoralis leaves were in favor of sodium and chloride, but against potassium, calcium and magnesium which were retained in plants. Sodium and chloride were excreted from special salt glands, which were scattered on the both leaf surfaces. In addition to salt glands, papillae were the most frequent epidermal structure found on A. littoralis leaves, and are likely involved in A. littoralis salt resistance.

Proteomic responses in shoots of the facultative halophyte Aeluropus littoralis (Poaceae) under NaCl salt stress.

Salinity is an environmental constraint that limits agricultural productivity worldwide. Studies on the halophytes provide valuable information to describe the physiological and molecular mechanisms of salinity tolerance. Therefore, because of genetic relationships of Aeluropus littoralis (Willd) Parl. with rice, wheat and barley, the present study was conducted to investigate changes in shoot proteome patterns in response to different salt treatments using proteomic methods. To examine the effect of salinity on A. littoralis proteome pattern, salt treatments (0, 200 and 400mM NaCl) were applied for 24h and 7 and 30 days. After 24h and 7 days exposure to salt treatments, seedlings were fresh and green, but after 30 days, severe chlorosis was established in old leaves of 400mM NaCl-salt treated plants. Comparative proteomic analysis of the leaves revealed that the relative abundance of 95 and 120 proteins was significantly altered in 200 and 400mM NaCl treated plants respectively. Mass spectrometry-based identification was successful for 66 out of 98 selected protein spots. These proteins were mainly involved in carbohydrate, energy, amino acids and protein metabolisms, photosynthesis, detoxification, oxidative stress, translation, transcription and signal transduction. These results suggest that the reduction of proteins related to photosynthesis and induction of proteins involved in glycolysis, tricarboxylic acid (TCA) cycle, and energy metabolism could be the main mechanisms for salt tolerance in A. littoralis. This study provides important information about salt tolerance, and a framework for further functional studies on the identified proteins in A. littoralis.

Insights into the physiological responses of the facultative halophyte Aeluropus littoralis to the combined effects of salinity and phosphorus availability.

In this work, we investigate the physiological responses to P deficiency (5µM KH2PO4=D), salt stress (400mM NaCl=C+S), and their combination (D+S) on the facultative halophyte Aeluropus littoralis to understand how plants adapt to these combined stresses. When individually applied, both P deficiency and salinity significantly restricted whole plant growth, with a more marked effect of the latter stress. However, the effects of the two stresses were not additive in plant biomass production since the response of plants to combined salinity and P deficiency was similar to that of plants grown under salt stress alone. In addition the observed features under salinity alone are kept when plants are simultaneously subjected to the combined effects of salinity and P deficiency such as biomass partitioning; the synthesis of proline and the K(+)/Na(+) selectivity ratio. Thus, increasing P availability under saline conditions has no significant effect on salt tolerance in this species. Plants cultivated under the combined effects of salinity and P deficiency exhibited the lowest leaf water potential. This trend was associated with a high accumulation of Na(+), Cl(-) and proline in shoots of salt treated plants suggesting the involvement of these solutes in osmotic adjustment. Proline could be involved in other physiological processes such as free radical scavenging. Furthermore, salinity has no significant effect on phosphorus acquisition when combined with a low P supply and it significantly decreased this parameter when combined with a sufficient P supply. This fact was probably due to salt's effect on P transporters. In addition, shoot soluble sugars accumulation under both P deficiency treatments with and without salt likely play an important role in the adaptation of A. littoralis plants to P shortage applied alone or combined with salinity. Moreover, there was a strong correlation between shoot and root intracellular acid phosphatase activity and phosphorus use efficiency which strengthens the assumption that intracellular acid phosphatase enzymes are involved in P remobilization in this species. Finally, our results showed that P availability has no significant effect on salt excretion in A. littorlais which suggests that independently of the P status in the plant, excretion remains priority over other functions requiring energy such as growth. This result could also indicate that salt excretion is not energy-dependent in this species.

Localization of potential ion transport pathways in vesicular trichome cells of Atriplex halimus L.

The secreting glandular trichomes are recognized as an efficient structure that alleviates salt effects on Atriplex halimus. They are found on buds, young green stems, and leaves. They occupy both the leaf surfaces and give them a whitish color. Their histogenesis and ultrastructure were investigated in the third young leaves. They appear in early stage of plant development and its initiation continuous until just the leaf final development state. Each trichome contains two parts; a stalk which has high electron opacity, embedded in epidermal cells, and bears a second one which is unicellular, called bladder cell and has a low electron density. The bladder cell appears as a huge vacuole and the well-reduced cytoplasm which is pushed close to the wall, contains only a few organelles. Concurrently, the use of silver chloride precipitation technique shows that, in secretion process, salt follows a symplasmatic pathway which is consolidated by the presence of numerous plasmodesmata between the stalk cell(s), and the bladder one and the neighboring mesophyll cells. In addition, according to lanthanum-tracer study, salt can be excreted apoplastically. In fact, the heavy element can be transported via endocytosis vesicles, and by Golgi, endoplasmic reticulum, and lysosome (G.E.R.L.) network toward the storage vacuoles.

ABA, GA(3), and nitrate may control seed germination of Crithmum maritimum (Apiaceae) under saline conditions.

Impaired germination is common among halophyte seeds exposed to salt stress, partly resulting from the salt-induced reduction of the growth regulator contents in seeds. Thus, the understanding of hormonal regulation during the germination process is a main key: (i) to overcome the mechanisms by which NaCl-salinity inhibit germination; and (ii) to improve the germination of these species when challenged with NaCl. In the present investigation, the effects of ABA, GA(3), NO(-)(3), and NH(+)(4) on the germination of the oilseed halophyte Crithmum maritimum (Apiaceae) were assessed under NaCl-salinity (up to 200 mM NaCl). Seeds were collected from Tabarka rocky coasts (N-W of Tunisia). The exogenous application of GA(3), nitrate (either as NaNO(3) or KNO(3)), and NH(4)Cl enhanced germination under NaCl salinity. The beneficial impact of KNO(3) on germination upon seed exposure to NaCl salinity was rather due to NO(-)(3) than to K(+), since KCl failed to significantly stimulate germination. Under optimal conditions for germination (0 mM NaCl), ABA inhibited germination over time in a dose dependent manner, but KNO(3) completely restored the germination parameters. Under NaCl salinity, the application of fluridone (FLU) an inhibitor of ABA biosynthesis, stimulated substantially seed germination. Taken together, our results point out that NO(-)(3) and GA(3) mitigate the NaCl-induced reduction of seed germination, and that NO(-)(3) counteracts the inhibitory effect of ABA on germination of C. maritimum.

Ultrastructure of Aeluropus littoralis leaf salt glands under NaCl stress.

The effects of salt uptake on the morphology and ultrastructure of leaf salt glands were investigated in Aeluropus littoralis plants grown for two months in the presence of 400 mM NaCl. The salt gland is composed of two linked cells, as observed in some other studied Poaceae species. The cap cell, which protrudes from the leaf surface, is smaller than the basal cell, which is embedded in the leaf mesophyll tissues and bears the former. The cuticle over the cap cell is frequently separated from the cell wall to form a cavity where salts accumulate prior to excretion. The basal cell cytoplasm contains an extensive intricate or partitioning membrane system that is probably involved in the excretion process, which is absent from the cap cell. The intricate membrane system seems to be elongated and heavily loaded with salt. The presence of 400 mM NaCl induced the disappearance of the collecting chamber over the glands and an increase in the number of vacuoles and their size in both gland cells. In the basal cell, salt greatly increased both the density and size of the intricate membrane system. The electron density of both gland cells observed under salt treatment reflects a high activity. All these changes probably constitute special adaptations for dealing with salt accumulation in the leaves. Despite the high salt concentration used, no serious damage occurred in A. littoralis salt gland ultrastructure, which consolidates the assumption that they are naturally designated for this purpose.

Salt impact on photosynthesis and leaf ultrastructure of Aeluropus littoralis.

The effects of salinity (400 mM NaCl) on growth, biomass partitioning, photosynthesis, and leaf ultrastructure were studied in hydroponically grown plants of Aeluropus littoralis (Willd) Parl. NaCl produced a significant inhibition of the main growth parameters and a reduction in leaf gas exchange (e.g. decreased rates of photosynthesis and stomatal conductance). However, NaCl salinity affected neither the composition of photosynthesis pigments nor leaf water content. The reduction in leaf gas exchange seemed to correlate with a decrease in mesophyll thickness as well as a severe disorganisation of chloroplast structure, with misshapen chloroplasts and dilated thylakoid membranes. Conspicuously, mesophyll chloroplasts were more sensitive to salt treatment than those of bundle sheath cells. The effects of NaCl toxicity on leaf structure and ultrastructure and the associated physiological implications are discussed in relation to the degree of salt resistance of A. littoralis.