Plant-specific environmental and developmental signals regulate the mismatch repair protein MSH6 in Arabidopsis thaliana

The DNA mismatch repair (MMR) is a postreplicative system that guarantees genomic stability by correcting mispaired and unpaired nucleotides. In eukaryotic nuclei, MMR is initiated by the binding of heterodimeric MutS homologue (MSH) complexes to the DNA error or lesion. Among these proteins, MSH2-MSH6 is the most abundant heterodimer. Even though the MMR mechanism and proteins are highly conserved throughout evolution, physiological differences between species can lead to different regulatory features. Here, we investigated how light, sugar, and/or hormones modulate Arabidopsis thaliana MSH6 expression pattern. We first characterized the promoter region of MSH6. Phylogenetic shadowing revealed three highly conserved regions. These regions were analyzed by the generation of deletion constructs of the MSH6 full-length promoter fused to the β-glucuronidase (GUS) gene. Combined, our in silico and genetic analyses revealed that a 121-bp promoter fragment was necessary for MSH6 expression and contained potential cis-acting elements involved in light- and hormone-responsive gene expression. Accordingly, light exposure or sugar treatment of four-day old A. thaliana seedlings triggered an upregulation of MSH6 in shoot and root apical meristems. Appropriately, MSH6 was also induced by the stem cell inducer WUSCHEL. Further, the stimulatory effect of light was dependent on the presence of phyA. In addition, treatment of seedlings with auxin or cytokinin also caused an upregulation of MSH6 under darkness. Consistent with auxin signals, MSH6 expression was suppressed in the GATA23 RNAi line compared with the wild type. Our results provide evidence that endogenous factors and environmental signals controlling plant growth and development regulate the MSH6 protein in A. thaliana.

6-benzylaminopurine causes endothelial dysfunctions to human umbilical vein endothelial cells and exacerbates atorvastatin-induced cerebral hemorrhage in zebrafish

6-benzylaminopurine (6-BA), a multifunctional plant growth regulator, which is frequently used worldwide to improve qualities of various crops, is an important ingredient in production of "toxic bean sprouts." Although there is no direct evidence of adverse effects, its hazardous effects, as well as joint toxicity with other chemicals, have received particular attention and aroused furious debate between proponents and environmental regulators. By use of human umbilical vein endothelial cells (HUVECs), adverse effects of 6-BA to human-derived cells were first demonstrated in this study. A total of 25-50 mg 6-BA/L inhibited proliferation, migration, and formation of tubular-like structures by 50% in vitro. Results of Western blot analyses revealed that exposure to 6-BA differentially modulated the MAPK signal transduction pathway in HUVECs. Specifically, 6-BA decreased phosphorylation of MEK and ERK, but increased phosphorylation of JNK and P38. In addition, 6-BA exacerbated atorvastatin-induced cerebral hemorrhage via increasing hemorrhagic occurrence by 60% and areas by 4 times in zebrafish larvae. In summary, 6-BA elicited toxicity to the endothelial system of HUVECs and zebrafish. This was due, at least in part, to discoordination of MAPK signaling pathway, which should pose potential risks to the cerebral vascular system.

Plant Regeneration via Adventitious Shoot Formation from Immature Zygotic Embryo Explants of Camelina

Camelina is an oil seed crop that is enjoying increasing interest because it has a particularly valuable fatty acid profile, is modest regarding its water and nutrient requirements, and is comparatively resilient to abiotic and biotic stress factors. The regeneration of plants from cells accessible to genetic manipulation is an essential prerequisite for the generation of genetically engineered plants, be it by transgenesis or genome editing. Here, immature embryos were used on the assumption that their incomplete differentiation was associated with totipotency. In culture, regenerative structures appeared adventitiously at the embryos' hypocotyls. For this, the application of auxin- or cytokinin-type growth regulators was essential. The formation of regenerative structures was most efficient when indole-3-acetic acid was added to the induction medium at 1 mg/L, zygotic embryos of the medium walking stick stage were used, and their hypocotyls were stimulated by pricking to a wound response. Histological examinations revealed that the formation of adventitious shoots was initiated by locally activated cell division and proliferation in the epidermis and the outer cortex of the hypocotyl. While the regeneration of plants was established in principle using the experimental line Cam139, the method proved to be similarly applicable to the current cultivar Ligena, and hence it constitutes a vital basis for future genetic engineering approaches.

Authenticating Emergent Adulterant 6-Benzylaminopurine in Bean Sprouts: Virtual Hapten Similarity Enhanced Immunoassay

6-Benzylaminopurine (6-BA), a plant growth regulator with cytokinin-like properties, was recently reported to be illegally used in bean sprouts to increase their commercial appearance. It is still nevertheless challenging to quickly detect this adulteration. In this work, four novel haptens (haptens 1-4) of 6-BA were rationally designed with computer-assisted modeling analysis and then synthesized for use as immunizing haptens to produce antibodies. One of two obtained antibodies showed high sensitivity and specificity toward 6-BA. Based on the most sensitive anti-6-BA antibody, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was performed, which demonstrated a 50% inhibition concentration (IC₅₀) of 1.18 μg/L and a limit of detection of 0.075 μg/L. The average recoveries of this icELISA for 6-BA of spiked samples ranged from 87.2 to 95.0% with a coefficient of variation of less than 8.7%. Furthermore, the blind samples were detected simultaneously by the method and HPLC-MS/MS, and the results showed good agreement with each other. Therefore, the proposed icELISA can facilitate the rapid surveillance screening of adulterated 6-BA in sprout vegetables.

Auxin and cytokinin synergism in micropropagation for mass production of Aloe vera

Aloe vera [Aloe vera (L.) Burm. f.] is considered a valuable medicinal plant worldwide due to its remarkable beneficial effects on human health. However, challenges in A. vera propagation hinder meeting the increasing demand in the health and beauty sectors. As an alternative method, in vitro propagation is crucial for the mass production of Aloe plants, which is a rapid method as well. Therefore, the present study aimed to establish an efficient micropropagation protocol for A. vera by in vitro optimization of the effect of different plant growth regulators (PGRs). For shoot proliferation, sterilized explants were inoculated on the Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) and thidiazuron (0.5, 1.0, 2.0, and 4.0 mg/l) in combination with 0.5 mg/l naphthaleneacetic acid (NAA). Subsequently, indole-3-butyric acid (IBA) (1.0, 2.0, and 3.0 mg/l) was used for root induction. It was found that the explants cultured on the MS medium supplemented with 4.0 mg/l BAP + 0.5 mg/l NAA showed the highest percentage of response (90 ± 1.29) for shoot induction within the minimum number of days (5 ± 0.33). The highest number of shoots (2.7 ± 0.36) and length of shoots (4.7 ± 0.42 cm) per explant were also observed with the same concentration of PGRs. However, the highest number of roots (3.2 ± 0.57), length of roots (5.67 ± 0.21 cm), and root induction (80 ± 1.97 %) were noticed within the minimum number of days (11 ± 0.79) on the MS medium supplemented with 1.0 mg/l IBA. Thus, the proposed method is a quick and effective approach for the mass propagation of A. vera with appropriate dosages of auxins and cytokinins, which may allow meeting the increasing commercial demand.

High-frequency adventitious shoot organogenesis from in vitro stem explants of Scutellaria araxensis Grossh

The present study introduced an in vitro shoot organogenesis protocol for the medicinal plant Scutellaria araxensis (Lamiaceae). Stem, leaf, and petiole explants were cultured in half-strength Murashige and Skoog (MS) medium containing different concentrations of 6-benzylaminopurine (BAP) alone or in combination with thidiazuron (TDZ), indole-3-butyric acid (IBA), or α-naphthalene acetic acid. Callus formation occurred from stem and petiole explants in most cultures; however, in leaf explants, it was observed only in cultures containing 0.5 mg/l BAP supplemented with TDZ at all concentrations. The highest frequency of indirect shoot induction (100 and 90%) with an average of 20.33 and 12 shoots per explant was observed in stem-derived calli cultured on half-strength MS medium containing 2.0 mg/l BAP plus 0.5 and 1.5 mg/l TDZ, respectively. The best direct shoot organogenesis (40%) was observed in stem explants cultured on half-strength MS medium containing 0.5 mg/l BAP and 0.5 mg/l IBA with a mean of 18 shoots per stem explant. The regenerated micro-shoots were elongated on a medium fortified with 0.5 mg/l gibberellic acid and then successfully rooted in half-strength MS medium supplemented with 0.5 mg/l IBA. The obtained plantlets were acclimatized in a growth chamber with a survival rate of 100%. This study is the first report of a simple and efficient in vitro shoot organogenesis and regeneration protocol for S. araxensis by using stem explants, which could be useful for the conservation, genetic manipulation, and exploitation of biological molecules of this valuable genetic source.

LF-NMR/MRI Determination of Different 6-Benzylaminopurine Concentrations and Their Effects on Soybean Moisture

In this study, we aimed to clarify the distribution and dynamics of water in the Xudou 20 soybean cultivar post-germination after culturing plants with various concentrations of 6-benzylaminopurine (6-BA). Low-field nuclear magnetic resonance and magnetic resonance imaging (LF-NMR/MRI), as well as principal component analysis (PCA), were used for the investigation. Results showed that low concentrations of 6-BA promoted soybean germination and high concentrations inhibited soybean germination, with 5 mg/l of 6-BA producing the most optimal conditions for growth. Moreover, the T ₂₂ determination of weakly bound water increased with increasing 6-BA concentration, and the PCA effectively distinguished soybeans cultured at different 6-BA concentrations. This study provides a method for the rapid detection of 6-BA concentration in bean sprouts and provides theoretical support and bean sprout quality assessment.

Seedlings

Copper (Cu) is an essential element involved in various metabolic processes in plants, but at concentrations above the threshold level, it becomes a potential stress factor. The effects of two different cytokinins, kinetin (KIN) and 6-benzylaminopurine (BAP), on chlorophyll a fluorescence parameters, stomatal responses and antioxidation mechanisms in castor (Ricinus communis L.) under Cu²⁺ toxicity was investigated. Ricinus communis plants were exposed to 80 and 160 μM CuSO₄ added to the growth medium. Foliar spraying of 15 μM KIN and BAP was carried out on these seedlings. The application of these cytokinins enhanced the tissue water status, chlorophyll contents, stomatal opening and photosynthetic efficiency in the castor plants subjected to Cu²⁺ stress. The fluorescence parameters, such as Fm, Fv/Fo, Sm, photochemical and non-photochemical quantum yields, energy absorbed, energy trapped and electron transport per cross-sections, were more efficiently modulated by BAP application than KIN under Cu²⁺ toxicity. There was also effective alleviation of reactive oxygen species by enzymatic and non-enzymatic antioxidation systems, reducing the membrane lipid peroxidation, which brought about a relative enhancement in the membrane stability index. Of the various treatments, 80 µM CuSO₄ + BAP recorded the highest increase in photosynthetic efficiency compared to other cytokinin treatments. Therefore, it can be concluded that BAP could effectively alleviate the detrimental effects of Cu²⁺toxicity in cotyledonary leaves of R. communis by effectively modulating stomatal responses and antioxidation mechanisms, thereby enhancing the photosynthetic apparatus’ functioning.

Melatonin mitigated circadian disruption and cardiovascular toxicity caused by 6-benzylaminopurine exposure in zebrafish

As a highly effective plant hormone, the overuse of 6-benzylaminopurine (6-BA) may pose potential threats to organisms and the environment. Melatonin is widely known for its regulation of sleep rhythm, and it also shows a beneficial effect in a variety of adverse situations. In order to investigate the harm of 6-BA to vertebrates and whether melatonin can reverse the toxicity induced by 6-BA, we analyzed the circadian rhythm and cardiovascular system of zebrafish, and further clarified the role of the thyroid endocrine system. The exposure of well-developed embryos started at 2 hpf, then 6-BA and/or melatonin were carried out. The results indicated that 6-BA disturbed the rhythmic activities of the larvae, increased wakefulness, correspondingly reduced their rest, and induced disrupted clock gene expression. Video analysis and qRT-PCR data found that zebrafish under 6-BA exposure showed obvious cardiovascular morphological abnormalities and dysfunction, and the mRNA levels of cardiovascular-related genes (nkx2.5, gata4, myl7, vegfaa and vegfab) were significantly down-regulated. In addition, altered thyroid hormone content and hypothalamus-pituitary-thyroid (HPT) axis-related gene expression were also clearly observed. 1umol/L of melatonin had little effect on zebrafish, but its addition could significantly alleviate the circadian disturbance and cardiovascular toxicity caused by 6-BA, and simultaneously played a regulatory role in thyroid system. Our research revealed the adverse effects of 6-BA on zebrafish larvae and the protective role of melatonin in circadian rhythm, cardiovascular and thyroid systems.

In Vitro Culture of Rosmarinus officinalis L. in a Temporary Immersion System: Influence of Two Phytohormones on Plant Growth and Carnosol Production

Emerging infectious diseases have become a major global problem with public health and economic consequences. It is an urgent need to develop new anti-infective therapies. The natural diterpene carnosol exhibit a wide variety of interesting antibacterial and antiviral properties, and it is considered a theoretical inhibitor of COVID-19 M^pro. However, this compound is present in the family Lamiaceae in low quantities. To obtain carnosol in concentrations high enough to develop pharmacological studies, we evaluated the efficiency of a micropropagation protocol of Rosmarinus officinalis using a solid medium and a temporary immersion system (TIS), as well as the effect of 6-benzylaminopurine (6-BAP) and α-naphthaleneacetic acid (NAA) on the growth of shoots. Moreover, we developed and validated an analytical method to quantify carnosol using the H-point standard additions method in the high-performance liquid chromatography diode array detector (HPLC-DAD). After 30 days of culture, TIS produced the maximum number of shoots per explant (24.33 ± 1.15) on a liquid medium supplemented with 6-BAP at 5.0 mg L⁻¹. Next, we also evaluated the effect of immersion time and frequency for TIS. After 72 days of culture, the best results were obtained with an immersion cycle of 1 min every 12 h, yielding 170.33 ± 29.40 shoots. The quantification of carnosol on the samples was performed at a flow rate of 1.2 mL min⁻¹ using binary isocratic mobile phase system 60:40 (v/v) 10 mM formic acid (pH 3.0) (A) and acetonitrile (B) on a reverse-phase column. The content of carnosol in the in vitro cultures was around 8-fold higher than in the wild plant. The present study represents an efficient alternative method to obtain carnosol for its pre-clinical and clinical development.

Cytokinin (6-benzylaminopurine) elevates lignification and the expression of genes involved in lignin biosynthesis of carrot

Carrot is a root crop consumed worldwide and has great nutritional qualities. It is considered as one of the ten most important vegetable crops. Cytokinins are an essential class of the plant hormones that regulate many processes of plant growth. Till now, the effects of cytokinin, BAP, on lignin biosynthesis and related gene expression profiles in carrot taproot is unclear. In order to investigate the effect of applied BAP on lignin-related gene expression profiles, lignin accumulation, anatomical structures, and morphological characters in carrot taproots. Carrot roots were treated with different concentrations of BAP (0, 10, 20, and 30 mg L^-1). The results showed that the application of BAP significantly increased plant length, shoot fresh weight, root fresh weight, and taproot diameter. In addition, BAP at 20 mg L^-1 or 30 mg L^-1 enhanced the average number of petioles. BAP treatment led to increased number and width of xylem vessels. The parenchyma cell numbers of pith were significantly induced in taproots treated with the BAP at a concentration of 30 mg L^-1. BAP significantly upregulated most of the expression levels of lignin biosynthesis genes, caused elevated lignin accumulation in carrot taproots. Our results indicate that BAP may play important roles in growth development and lignification in carrot taproots. Our results provide a valuable database for more studies, which may focus on the regulation of root lignification via controlling cytokinin levels in carrot taproots.

A New Strategy to Increase Production of Genoprotective Bioactive Molecules from Cotyledon-Derived Silybum marianum L. Callus

There is a need to enhance the production of bioactive secondary metabolites and to establish new production systems, e.g., for liver-protective compounds of Silybum marianum seeds. Quantifying and identifying the produced phytochemicals, and examining their protective effects against genotoxic agents, is of great interest. This study established a protocol for the qualitative and quantitative production of hepatoprotective compounds in cotyledon-derived Silybum marianum callus through optimized supplementation of the MS medium with the growth regulators 2,4-D, benzylaminopurine, myoinositol, and asparagine. High-performance liquid chromatography (HPLC) coupled with electrospray ionisation mass spectrometry (ESI-MS) allowed for identification and quantification of the produced compounds. None of the growth medium combinations supported a detectable production of silymarin. Instead, the generated calli accumulated phenolic acids, in particular chlorogenic acid and dicaffeoylquinic acid, as revealed by HPLC and mass spectrometric analysis. 4-Nitro-o-phenylenediamine (NPD) was employed in the AMES-test with Salmonella typhimurium strain TA98 because it is a potent mutagen for this strain. Results revealed that callus extract had a high anti-genotoxic activity with respect to standard silymarin but more evident with respect seed extract. The callus produced chlorogenic acid and dicaffeoylquinic acid, which revealed higher bioactivity than silymarin. Both compounds were not formed or could not be detected in the seeds of Silybum marianum Egyptian ecotype.

Production of Biopharmaceuticals in Nicotiana benthamiana-Axillary Stem Growth as a Key Determinant of Total Protein Yield

Data are scarce about the influence of basic cultural conditions on growth patterns and overall performance of plants used as heterologous production hosts for protein pharmaceuticals. Higher plants are complex organisms with young, mature, and senescing organs that show distinct metabolic backgrounds and differ in their ability to sustain foreign protein expression and accumulation. Here, we used the transient protein expression host Nicotiana benthamiana as a model to map the accumulation profile of influenza virus hemagglutinin H1, a clinically promising vaccine antigen, at the whole plant scale. Greenhouse-grown plants submitted to different light regimes, submitted to apical bud pruning, or treated with the axillary growth-promoting cytokinin 6-benzylaminopurine were vacuum-infiltrated with agrobacteria harboring a DNA sequence for H1 and allowed to express the viral antigen for 7 days in growth chamber under similar environmental conditions. Our data highlight the importance of young leaves on H1 yield per plant, unlike older leaves which account for a significant part of the plant biomass but contribute little to total antigen titer. Our data also highlight the key contribution of axillary stem leaves, which contribute more than 50% of total yield under certain conditions despite representing only one-third of the total biomass. These findings underline the relevance of both considering main stem leaves and axillary stem leaves while modeling heterologous protein production in N. benthamiana. They also demonstrate the potential of exogenously applied growth-promoting hormones to modulate host plant architecture for improvement of protein yields.

Transcriptomic Mechanism of the Phytohormone 6-Benzylaminopurine (6-BAP) Stimulating Lipid and DHA Synthesis in Aurantiochytrium sp

The phytohormone 6-benzylaminopurine (6-BAP) significantly improves lipid synthesis of oleaginous microorganisms with the great potential applied in lipid production. In the current study, the lipid and DHA productions in oleaginous Aurantiochytrium sp. were found to be improved by 48.7% and 55.3%, respectively, induced by 6-BAP treatments. Then, using high-throughput RNA-seq technology, the overall de novo assembly of the cDNA sequence data generated 53871 unigenes, and 15902 of these were annotated in at least one database. The comparative transcriptomic profiles of cells with and without 6-BAP treatments revealed that a total of 717 were differently expressed genes (DE), with 472 upregulated and 245 downregulated. Further annotation and categorization indicated that some DE genes were involved in pathways crucial to lipid and DHA productions, such as fatty acid synthesis, central carbon metabolism, transcriptional factor, signal transduction, and mevalonate pathway. A regulation mode of 6-BAP, in turn, perception and transduction of 6-BAP signal, transcription factor, expression regulations of the downstream genes, and metabolic changes, respectively, was put forward for the first time in the present study. This research illuminates the transcriptomic mechanism of phytohormone stimulation of lipid and DHA production in an oleaginous microorganism and provides the potential targets modified using genetic engineering for improving lipid and DHA productivity.

Exogenous salicylic acid and cytokinin alter sugar accumulation, antioxidants and membrane stability of faba bean

This research was conducted in a greenhouse to evaluate the effects of exogenous application of salicylic acid (SA) (1 mM) and 6-benzylaminopurine (BAP) (50 μM) on physiological performance of faba bean (Vicia faba) under different levels of NaCl salinity (0, 4, 8 and 12 dS/m). The experiment was arranged as factorial on the bases of randomized complete block design in three replications. Leaf Na⁺ content, root and leaf soluble sugars, antioxidant enzymes activities such as catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and lipid peroxidation increased, but K⁺, K⁺/Na⁺ and membrane stability index (MSI) decreased as a result of salt stress. However, foliar sprays of BAP and particularly SA reduced Na⁺ content and lipid peroxidation, while enhanced the K⁺ content, K⁺/Na⁺, soluble sugars, antioxidant enzymes activities and MSI under different levels of salinity. It was, therefore, concluded that exogenous application of these growth regulators (GR) can considerably improve salt tolerance and physiological performance of faba bean.

Phytochemical investigation of natural and in vitro raised Vṛddhadāruka plants

Background:

Argyreia nervosa commonly known as elephant creeper (English) and Vṛddhadāruka (Sanskrit) is a woody climber that belongs to the family Convolvulaceae. Seeds of this plant contain hallucinogens including ergot alkaloids and a naturally occurring lysergic acid amide. Traditionally the plant is used in the treatment of gonorrhea, strangury, chronic ulcers, diabetes, anemia and cerebral disorders. The plant is also used as appetitiser, brain tonic, cardiotonic, aphrodisiac. It possesses anti-inflammatory, immunomodulatory, antibacterial, antiviral and antifungal activities.

Objective:

To give an account of information on in vitro regeneration and phytochemical analysis of the plant.

Materials and Methods:

Nodal explants were selected for in vitro regeneration. Different aerial parts viz., seeds, natural and in vitro leaf, stem and callus were dried and extracted with different solvents and were subjected to various phytochemical analyses.

Results:

Different concentrations of 6-benzylaminopurine showed shoot and root initiation. The study of phytochemical screening of different extracts showed the presence of bioactive substances like flavonoids, alkaloids, terpenoids, etc.

Conclusion:

The study will provide an efficient in vitro protocol for micropropagation as an alternative method to conserve the plant and shows the presence of some important secondary metabolites in the nature grown and in vitro raised plants which can be useful for treatment of various diseases.

Effect of copper on pro- and antioxidative reactions in radish (Raphanus sativus L.) in vitro and in vivo

The generation of superoxide radicals, lipid peroxidation (as measured by malone dialdehyde formation) and the activity of selected antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase) were assessed in radish (Raphanus sativus L.), in response to elevated concentrations of copper ions in the culture medium in vitro and in vivo. Experiments were performed on 7-day-old seedlings and 5-week-old calluses grown on media supplemented with CuSO4 in concentrations of 10, 100 and 1000μМ. The exposure to elevated Cu concentrations in the medium significantly reduced both callogenesis and the proliferation of radish calluses in vitro. Cu treatment resulted in the increased generation of the superoxide radical (O2(-)) in radish seedlings and calluses indicating the occurrence of oxidative stress in radish cells, whereas the level of lipid peroxidation (LPO) remained unchanged. Both in calluses and in radish seedlings in vivo, the relative level of oxidative stress was maximal at micromolar Cu concentrations and became attenuated with increasing Cu concentrations. Stronger oxidative stress occurred in the radish seedlings in vivo, compared with radish calluses in vitro. The observed lower sensitivity of calluses to Cu-induced oxidative stress and their ability to proliferate upon exposure to Cu concentrations of up to 1000μМ demonstrate the potential of in vitro cell-selection to obtain metal-tolerant radish plant lines.

Characterization of the response of in vitro cultured Myrtus communis L. plants to high concentrations of NaCl

Effect of salt stress was examined in in vitro shoot cultures of Myrtus communis L. a species of the Mediterranean maquis. To determine the effects of high salt concentrations on myrtle plantlets and contribute toward understanding the mechanisms adopted from this species to counteract soil salinity, in vitro rooted shoots were transferred to a liquid culture medium containing 0, 125 or 250 mM NaCl for 30 days. After 15 and 30 days of in vitro culture, shoot and root growth, chlorosis and necrosis extension, chlorophylls, carotenoids, proline, arginine, cysteine and total sugars content, as well as guaiacol peroxidase (G-POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) activities were determined. In treated plants shoot and root growth, as well as chlorophyll content, significantly decreased, while carotenoids content was not affected by the NaCl treatment. Among osmolytes, proline did not significantly increase, arginine and cysteine decreased, while total sugars were found to be higher in the treated plants than in the control. Enhancement of G-POD and APX activities was positively related to increasing salt concentrations in the culture media, regardless of the exposure time. Salt-treated plants did not show significant changes in lipid peroxidation or DNA fragmentation after 30 days salt treatment, regardless of the NaCl concentrations applied. The results represent a contribution towards understanding the mechanisms adopted by this species to high salinity.

Isolation and expression profiling of GhNAC transcription factor genes in cotton (Gossypium hirsutum L.) during leaf senescence and in response to stresses

NAC (NAM, ATAF, and CUC) is a plant-specific transcription factor family with diverse roles in plant development and stress regulation. In this report, stress-responsive NAC genes (GhNAC8-GhNAC17) isolated from cotton (Gossypium hirsutum L.) were characterised in the context of leaf senescence and stress tolerance. The characterisation of NAC genes during leaf senescence has not yet been reported for cotton. Based on the sequence characterisation, these GhNACs could be classified into three groups belonging to three known NAC sub-families. Their predicted amino acid sequences exhibited similarities to NAC genes from other plant species. Senescent leaves were the sites of maximum expression for all GhNAC genes except GhNAC10 and GhNAC13, which showed maximum expression in fibres, collected from 25 days post anthesis (DPA) plants. The ten GhNAC genes displayed differential expression patterns and levels during natural and induced leaf senescence. Quantitative RT-PCR and promoter analyses suggest that these genes are induced by ABA, ethylene, drought, salinity, cold, heat, and other hormonal treatments. These results support a role for cotton GhNAC genes in transcriptional regulation of leaf senescence, stress tolerance and other developmental stages of cotton.

Growth and photosynthetic responses to copper in wild grapevine

The present study evaluates the tolerance and accumulation potential of Vitis vinifera ssp. sylvestris under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0-23mmolL(-1)) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also measured the total copper, nitrogen, phosphorus, sulphur, calcium, magnesium, iron, potassium and sodium concentrations in the plant tissues. All the experimental plants survived even with external Cu concentrations as high as 23mmolL(-1) (1500mg Cu L(-1)), although the excess of metal resulted in a biomass reduction of 35%. The effects of Cu on growth were linked to a reduction in net photosynthesis, which may be related to the effect of the high concentration of the metal on photosynthetic electron transport. V. vinifera ssp. sylvestris survived with leaf Cu concentrations as high as 80mgkg(-1) DW and growth parameters were unaffected by leaf tissue concentrations of 35mg Cu kg(-1) DW. The results of our study indicate that plants of V. vinifera ssp. sylvestris from the studied population are more tolerant to Cu than the commercial varieties of grapevine that have been studied in the literature, and could constitute a basis for the genetic improvement of Cu tolerance in grapevine.

Plant regeneration via somatic embryogenesis and shoot organogenesis from immature cotyledons of Camellia nitidissima Chi

Camellia nitidissima Chi (Theaceae) is a world-famous economic and ornamental plant with golden-yellow flowers. It has been classified as one of the rarest and most endangered plants in China. Our objective was to induce somatic embryogenesis, shoot organogenesis and plant regeneration for C. nitidissima. Three types of callus (whitish, reddish and yellowish) were induced from immature cotyledons on improved woody plant medium (WPM) with different plant growth regulators (PGRs). Among the callus, whitish callus was induced by 4.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and reddish and yellowish callus were induced by strongly active cytokinins, thidiazuron (TDZ) or 6-benzylaminopurine (BAP), singly or combined with weakly active auxin, α-naphthaleneacetic acid (NAA). The embryogenic callus could differentiate into somatic embryos, nodular embryogenic structures (large embryo-like structures) or adventitious shoots depending on the PGR used in WPM. BAP was best for adventitious buds and zeatin was best for somatic embryogenesis while kinetin (Kt) was best for the formation of nodular embryogenic structures. The three regeneration pathways often occurred in the same embryogenic callus clumps. Most shoots (80.0%) developed roots in WPM supplemented with 24.6 μM IBA and 0.3 μM NAA while 47.5% of somatic embryos could germinate directly and develop into plantlets on induction medium supplemented with 0.9 μM BAP and 0.1 μM NAA. The nodular embryogenic structures could be sub-cultured and cyclically developed in one of two differentiation pathways: shoot organogenesis or somatic embryogenesis. Plantlets derived from shoot buds rooted and somatic embryos germinated when transplanted into soil in a greenhouse; 66.7% of plantlets from shoot culture and 78.6% of plantlets from somatic embryos survived after 8 weeks' acclimatization.

Evaluation of genetic fidelity among micropropagated plants of Gloriosa superba L. using DNA-based markers--a potential medicinal plant

Malabar glory lily (Gloriosa superba L.) is a medicinally potent plant species used for the production of alkaloid colchicine. With ever increasing demand, there is a pressing need to conserve it through biotechnological approaches. A large number of complete plantlets were obtained by direct regeneration from the non-dormant tuber explants on Murashige and Skoog (MS) medium supplemented with 2.0 mg/l 6-benzylaminopurine (BAP)+0.5 mg/l α-naphthalene acetic acid (NAA). Large number of plants can be produced in vitro under aseptic conditions, but there is always a danger of producing somaclonal variants by tissue culture technology. Thus, the genetic stability of micropropagated clones was evaluated using random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) analysis. During the study a total of 80 (50 RAPD and 30 ISSR) primers were screened, out of which 10 RAPD and 7 ISSR primers produced a total of 98 (49 RAPD and 49 ISSR) clear, distinct and reproducible amplicons. The amplification products of the regenerated plants showed similar banding patterns to that of the mother plant thus demonstrating the homogeneity of the micropropagated plants. This is the first report that evaluates the use of genetic markers to establish genetic fidelity of micropropagated G. superba using RAPD and ISSR, which can be successfully applied for the mass multiplication, germplasm conservation and further genetic transformation assays for colchicine production to meet the ever increasing demand of this medicinally potent plant for industrial and pharmaceutical uses.

An efficient plant regeneration protocol from callus cultures of Citrus jambhiri Lush

Citrus jambhiri Lush. (family Rutaceae), commonly known as 'rough lemon', is one of the favourite rootstocks for lemons, oranges, mandarins, grape fruits and kinnows in Punjab. The present investigation deals with development of an efficient miropropagation protocol for Citrus jambhiri Lush. using cotyledons as explant. Maximum callus induction (91.66 %) was observed on MS medium supplemented with 2,4-D (2 mg/L) in combination with ME (500 mg/L). Green healthy calli were cut into small pieces and cultured on MS medium for regeneration. Maximum shoot regeneration (87.50 %) was observed with BA (3 mg/L). Effect of increasing age of callus was also studied which showed that callus retained regeneration capacity (58.33 %) even after 420 days of culture. Regenerated shoots were separated out and cultured on rooting medium. Maximum rooting response (91.67 %) was observed on half strength MS medium supplemented with NAA (0.5 mg/L). After hardening and acclimatization the plantlet were transferred to the field and showed 67 % survival.

In vitro direct shoot regeneration from proximal, middle and distal segment of Coleus forskohlii leaf explants

Coleus forskohlii is an endangered multipurpose medicinal plant that has widespread applications. In spite of this, there have been few attempts to propagate its cultivation in India. The present communication presents an in vitro rapid regeneration method using leaf explants of Coleus forskohlii through direct organogenesis. Leaf explants that were excised into three different segments i.e. proximal (P), middle (M) and distal (D) were cultured on Murashige and Skoog (MS) basal medium supplemented with cytokinins. MS Media containing 5.0 mg L(-1) BAP (6-Benzylaminopurine) promoted regeneration of multiple shoots through direct organogenesis from the leaf, which were further elongated on MS media augmented with 0.1 mg L-1 BAP and 0.1 mg L(-1) IAA (Indole-3-acetic acid), cytokinin and auxin combination. Regenerated and elongated shoots, when transferred to ose resulted in profuse rooting plants that were transferred to soil after acclimatization and maintained in a green house. The current protocol offers a direct, mass propagation method bypassing the callus phase of C. forskohlii and is suitable for conservation, large-scale commercial cultivation, and genetic transformation with agronomically desirable traits.

Pod set related to photosynthetic rate and endogenous ABA in soybeans subjected to different water regimes and exogenous ABA and BA at early reproductive stages

BACKGROUND AND AIMS

The physiological reasons for reduced pod set in soybean (Glycine max) caused by drought during anthesis are not established. The objective of this study was to investigate the involvement of photosynthetic rate (A), pod endogenous abscisic acid (ABA) and exogenously applied ABA and 6-benzylaminopurine (BA) in regulating pod set in soybean during drought.

METHODS

Two pot experiments were done in a controlled-environment glasshouse. In expt I, soybeans were either well-watered (WW) or droughted by withholding water from 4 d before to 4 d after anthesis (DAA). In expt II, soybeans were drought-stressed (DS) from -4 to 4 DAA. From -2 to 4 DAA, some of the WW and DS plants were treated with 0.1 mm ABA or 1 mm BA.

KEY RESULTS

Drought stress decreased A, but increased pod ABA concentration ([ABA]). Pod set decreased only when A had decreased by 40 %, and pod [ABA] had increased 1.5-fold. Beyond the thresholds, pod set correlated positively with A and negatively with pod [ABA]. Exogenously applied ABA decreased A and pod set in WW plants, whilst it increased A and pod set in DS plants; exogenous BA had opposite effects. In these plants, pod set correlated linearly with A.

CONCLUSIONS

Drought-induced decrease in A is significant in inducing pod abortion, probably as a consequence of carbohydrate deprivation. The effects of ABA and BA on pod set may be partially due to their effects on photosynthate supply.

A simple and efficient plant regeneration system for leaf protoplasts ofNierembergia repens by inducing single shoots on the microcolonies

A simple and efficient protocol for plant regeneration from mesophyll protoplasts ofNierembergia repens is described. The protoplasts divided in modified half-strength MS (/12 MS) medium containing benzylaminopurine (BA) and a-naphthaleneacetic acid (NAA) and formed visible colonies after 2 weeks which produced single adventitious shoots 4 weeks later. Plating efficiency (11.2%), percent colony formation (0.84%), and the number of shoot-forming colonies (368/dish) were highest in /12 MS containing 0.1 mg/l BA and 0.05 mg/l NAA. However, the percentage of colonies with shoot formation was highest (31.8%) in /12 containing 0.05 mg/l BA and 0.01 mg/l NAA. Almost all of the remaining colonies (97.5%) also regenerated shoots upon transfer onto MS medium containing 0.05 mg/l BA. The shoots with 2-3 leaves readily rooted 3-5 days after insertion in /12MS lacking plant growth regulators. Regenerated plantlets were easily established in soil 50 days after protoplast isolation. All the regenerants were normal and possessed diploid chromosome numbers.