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In the present study, nanoscale micronutrient iron (α-Fe2O3) has been prepared via co-precipitation using marine macro alga Turbinaria ornata. The nanoscale micronutrient iron has been used as priming agent for enhancing seed germination, seed quality, uptake, translocation, physiological effects and yield level of rice and maize crops. The physico-chemical characterization techniques results showed the successful preparation of nanoscale micronutrient iron. Seeds primed with nanoscale micronutrient iron at 25 mg/L significantly enhanced the seed germination and seedling parameters in comparison with conventional hydro-priming. ROS production in germinating nano-primed seeds of rice and maize enhanced the seed germination better than the conventional hydro-priming. Uptake and distribution of nanoscale micronutrient iron in rice and maize seedlings were studied using HR-SEM & ICP-MS analysis. Foliar application of low concentration (10 mg/L) nanoscale micronutrient iron under field conditions significantly increased the chlorophyll content, yield attributes of rice and maize crops.

With climate warming, drought becomes a vital challenge for agriculture. Extended drought periods affect plant-pathogen interactions. We demonstrate an interplay in tomato between drought and infection with tomato yellow leaf curl virus (TYLCV). Infected plants became more tolerant to drought, showing plant readiness to water scarcity by reducing metabolic activity in leaves and increasing it in roots. Reallocation of osmolytes, such as carbohydrates and amino acids, from shoots to roots suggested a role of roots in protecting infected tomatoes against drought. To avoid an acute response possibly lethal for the host organism, TYLCV down-regulated the drought-induced activation of stress response proteins and metabolites. Simultaneously, TYLCV promoted the stabilization of osmoprotectants' patterns and water balance parameters, resulting in the development of buffering conditions in infected plants subjected to prolonged stress. Drought-dependent decline of TYLCV amounts was correlated with HSFA1-controlled activation of autophagy, mostly in the roots. The tomato response to combined drought and TYLCV infection points to a mutual interaction between the plant host and its viral pathogen.

Nanotechnology based fertilizer production possessing the desired chemical composition, can improve plant nutrition and may reduce the environmental impact and enhance the plant productivity. In this work, we have demonstrated the green preparation and characterization of nano iron (γ-Fe2O3) and zinc (ZnO), and the subsequent agro-morphological modification (germination, shoot length, root length, seedling length, vigor index and dry matter production (DMP) (fresh and dry weight), the effect on the crop productivity (1000 grain weight, seed length, seed thickness, seed width) and the mechanism of uptake in rice (Oryza sativa) and maize (Zea mays L.). The highest seed germination percentage (100%) and seedling vigor index values (27 500 and 36 500) were observed after using 500 ppm of nanoscale γ-Fe2O3 treatment in rice and maize, respectively. In the case of nanoscale ZnO, the highest seed germination percentages (100% and 99%) and seedling vigor index values (32 400 and 33 660) were observed at 1000 and 2000 ppm in rice and maize seeds, respectively. The results of the micro plot field studies revealed that yield attributes such as the total grain weight (g m−2), 1000 grain weight, seed length, seed thickness, seed width and yield (kg ha−1) were also highly influenced by the foliar application of nanoscale γ-Fe2O3 (500 ppm) and ZnO (750 ppm) in rice and maize, respectively.

In the present study, nanoscale micronutrient iron (α-Fe

Plant behavior and response to environmental stimuli has tremendous importance in science and agriculture. In particular, a plant’s root continuously senses changes in the environment, and responds in ways that optimize dynamically different essential parameters like its stability, and adequate food and water supplies. Some of the plant behavioral changes in response to environmental changes, like water shortage, can be reversible, and after certain “stress” time, the plant can get back to its normal behavioral patterns. In other cases, the plant behavior after the stress stimulus ends, is changed, due to effects on internal mechanisms, facilitating long-term behavioral changes. The main aim of this work is to derive a preliminary physical model and analysis tools to quantify the behavioral changes of a plant in response to a stimuli. To demonstrate the model, we examined, without loss of generality, the change in plant growth rate in response to electrical simuli. We showed how the suggested plant behavioral model can assist in computational analysis of short and long term plant response to changing stimuli, construct a common baseline for comparison with other stimuli, and derive new quantitative measurements that can be correlated with internal plant mechanism and assist in assessing behavioral plant patterns and in the design of more efficient agricultural technologies

Salinity impairs seed germination and seedling establishment. We investigated the role of Arabidopsis (Arabidopsis thaliana) CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR 6 (CAMTA6) in salinity stress responses during early germination. Compared with the wild type, the camta6-4 and camta6-5 mutants were more tolerant to NaCl and abscisic acid (ABA) and accumulated less Na(+). In contrast, 4- to 11-d-old camta6 seedlings were more sensitive to NaCl. In camta6, expression of HIGH-AFFINITY K(+) TRANSPORTER1 (AtHKT1;1), encoding an Na(+)/K(+) transporter, was restricted to the radicles and was not enhanced by NaCl or ABA. During germination, the camta6 hkt1 double mutant was as sensitive as the wild type and hkt1 to NaCl, suggesting that HKT1;1 is crucial for the salt tolerance of camta6. An ABA response element in the HKT1;1 promoter was found to be indispensable for the enhanced expression of the gene in response to NaCl and to ABA. Transcriptome analysis of the wild type and camta6-5 with and without salt treatment revealed 1,020 up-regulated and 1,467 down-regulated salt-responsive genes in the wild type. Among these, 638 up-regulated and 1,242 down-regulated genes were classified as CAMTA6-dependent. Expression of several known salt stress-associated genes, including SALT OVERLY SENSITIVE1 and Na(+)/H(+) ANTIPORTER, was impaired in camta6 mutants. Bioinformatics analysis of the 5′ upstream sequences of the salt-responsive CAMTA6-dependent up-regulated genes revealed the CACGTGTC motif as the most prominent element, representing an ABA response element and a potential CAMTA-binding site. We suggest that CAMTA6 regulates, directly or indirectly, the expression of most of the salt-responsive genes in germinating seeds, including genes that are crucial for Na(+) homeostasis and salt stress tolerance.

Significance Plant roots grow toward water, a phenomenon termed hydrotropism. The nature of the root signal that governs hydrotropism is elusive and remains to be elucidated. Here, we show that, in response to water potential differences across the root tip, a slow, asymmetric long-distance Ca2+ signal is transmitted via the phloem to the elongation zone, where it is asymmetrically distributed across the root to promote root curvature. Furthermore, we demonstrate that the hydrotropism-associated protein MIZ1 plays a role in generating the Ca2+ signal by its direct binding to and inhibition of ECA1, an endoplasmic reticulum Ca2+ pump, which resembles the animal sarco/endoplasmic reticulum Ca2+-ATPases (SERCAs). This study elucidates the mechanism underlying systemic Ca2+ signaling in plant roots, which is essential for water tracking., Ever since Darwin postulated that the tip of the root is sensitive to moisture differences and that it “transmits an influence to the upper adjoining part, which bends towards the source of moisture” [Darwin C, Darwin F (1880) The Power of Movement in Plants, pp 572–574], the signal underlying this tropic response has remained elusive. Using the FRET-based Cameleon Ca2+ sensor in planta, we show that a water potential gradient applied across the root tip generates a slow, long-distance asymmetric cytosolic Ca2+ signal in the phloem, which peaks at the elongation zone, where it is dispersed laterally and asymmetrically to peripheral cells, where cell elongation occurs. In addition, the MIZ1 protein, whose biochemical function is unknown but is required for root curvature toward water, is indispensable for generating the slow, long-distance Ca2+ signal. Furthermore, biochemical and genetic manipulations that elevate cytosolic Ca2+ levels, including mutants of the endoplasmic reticulum (ER) Ca2+-ATPase isoform ECA1, enhance root curvature toward water. Finally, coimmunoprecipitation of plant proteins and functional complementation assays in yeast cells revealed that MIZ1 directly binds to ECA1 and inhibits its activity. We suggest that the inhibition of ECA1 by MIZ1 changes the balance between cytosolic Ca2+ influx and efflux and generates the cytosolic Ca2+ signal required for water tracking.

The widely accepted Cholodny-Went theory posits that asymmetrical auxin redistribution is required for tropic growth of plant organs. We demonstrate, using the sensitive auxin-sensor protein DII-VENUS that, in the presence and absence of auxin polar transport inhibitors, root tropism toward moisture (hydrotropism) does not involve auxin redistribution. Moreover, highly specific auxin signaling antagonists accelerate hydrotropism. Thus, hydrotropism is an exception to the Cholodny-Went theory.

A plant's ability to cope with salt stress is highly correlated with their ability to reduce the accumulation of sodium ions in the shoot. Arabidopsis mutants affected in the ABSCISIC ACID INSENSITIVE (ABI) 4 gene display increased salt tolerance, whereas ABI4-overexpressors are hypersensitive to salinity from seed germination to late vegetative developmental stages. In this study we demonstrate that abi4 mutant plants accumulate lower levels of sodium ions and higher levels of proline than wild-type plants following salt stress. We show higher HKT1;1 expression in abi4 mutant plants and lower levels of expression in ABI4-overexpressing plants, resulting in reduced accumulation of sodium ions in the shoot of abi4 mutants. HKT1;1 encodes a sodium transporter which is known to unload sodium ions from the root xylem stream into the xylem parenchyma stele cells. We have shown recently that ABI4 is expressed in the root stele at various developmental stages and that it plays a key role in determining root architecture. Thus ABI4 and HKT1;1 are expressed in the same cells, which suggests the possibility of direct binding of ABI4 to the HKT1;1 promoter. In planta chromatin immunoprecipitation and in vitro electrophoresis mobility shift assays demonstrated that ABI4 binds two highly related sites within the HKT1;1 promoter. These sites, GC(C/G)GCTT(T), termed ABI4-binding element (ABE), have also been identified in other ABI4-repressed genes. We therefore suggest that ABI4 is a major modulator of root development and function.

The default growth pattern of primary roots of land plants is directed by gravity. However, roots possess the ability to sense and respond directionally to other chemical and physical stimuli, separately and in combination. Therefore, these root tropic responses must be antagonistic to gravitropism. The role of reactive oxygen species (ROS) in gravitropism of maize and Arabidopsis (Arabidopsis thaliana) roots has been previously described. However, which cellular signals underlie the integration of the different environmental stimuli, which lead to an appropriate root tropic response, is currently unknown. In gravity-responding roots, we observed, by applying the ROS-sensitive fluorescent dye dihydrorhodamine-123 and confocal microscopy, a transient asymmetric ROS distribution, higher at the concave side of the root. The asymmetry, detected at the distal elongation zone, was built in the first 2 h of the gravitropic response and dissipated after another 2 h. In contrast, hydrotropically responding roots show no transient asymmetric distribution of ROS Decreasing ROS levels by applying the antioxidant ascorbate, or the ROS-generation inhibitor diphenylene iodonium attenuated gravitropism while enhancing hydrotropism. Arabidopsis mutants deficient in Ascorbate Peroxidase 1 showed attenuated hydrotropic root bending. Mutants of the root-expressed NADPH oxidase RBOH C, but not rbohD, showed enhanced hydrotropism and less ROS in their roots apices (tested in tissue extracts with Amplex Red). Finally, hydrostimulation prior to gravistimulation attenuated the gravistimulated asymmetric ROS and auxin signals that are required for gravity-directed curvature. We suggest that ROS, presumably H2O2, function in tuning root tropic responses by promoting gravitropism and negatively regulating hydrotropism.

Arabidopsis thaliana is frequently grown on semisolid medium in Petri dishes, for various experiments that usually consist of two stages on two distinct growth media. Seedlings are germinated under favorable conditions followed by their transfer to another medium containing the given treatment(s). This often causes secondary effects on seedlings due to root shock, or direct and unavoidable contact of the shoot with the second medium. We have developed a simple and efficient method for the transfer of seedlings grown on semisolid medium with minimal damage. In this double-agar-layer method, seeds are germinated on a thin growth-medium-containing agar layer. Subsequently, medium blocks containing the embedded seedlings are excised and placed on the second semisolid medium supplemented with the treatment agent. Differential agar concentrations allow easy penetration of the roots into the second medium, but do not allow the shoots to come into contact with it. This unique method offers several advantages over others that are in common use, in which the seedlings are individually transferred to the second medium or alternatively grown on transfer-carrier matrices, such as filter paper, mesh and cellophane. In the presented method, the entire root system faces the growth medium, the shoots are surrounded by air at all growth stages and transfer of the seedlings is much easier. In addition, a large number of seedlings can be transferred in a single step, without stressing the plants or damaging the delicate root system. This method can also be applied to other plant species grown on semisolid media.

Key steps in a plant's development and adaptation to the environment are the initiation and development of lateral roots (LRs). LR development is regulated by auxin, the major plant hormone promoting LR formation, its counteracting hormones cytokinin, and abscisic acid (ABA). Here, we show that mutating ABSCISIC ACID INSENSITIVE4 (ABI4), which encodes an ABA-regulated AP2 domain transcription factor, results in an increased number of LRs. We show that ABI4 is expressed in roots and that its overexpression impairs LR development. Root expression of ABI4 is enhanced by ABA, and cytokinin and is repressed by auxin. Using hormone response promoters, we show that ABI4 also affects auxin and cytokinin profiles in the root. Furthermore, LR development in abi4 mutants is not altered or inhibited by cytokinin or ABA. Expression of the auxin-efflux carrier protein PIN1 is reduced in ABI4 overexpressors, enhanced in abi4 mutants, and is less sensitive to inhibition by cytokinin and ABA in abi4 mutants than in wild-type plants. Transport levels of exogenously applied auxin were elevated in abi4 mutants and reduced in ABI4 overexpressors. We therefore suggest that ABI4 mediates ABA and cytokinin inhibition of LR formation via reduction of polar auxin transport and that the resulting decrease in root auxin leads to a reduction in LR development.

The manipulation of transacting factors is commonly used to achieve a wide change in the expression of a large number of genes in transgenic plants as a result of a change in the expression of a single gene product. This is mostly achieved by the overexpression of transactivator or repressor proteins. In this study, it is demonstrated that the overexpression of an exogenous DNA-binding protein can be used to compete with the expression of an endogenous transcription factor sharing the same DNA-binding sequence. Arabidopsis was transformed with cDNA encoding tomato abscisic acid stress ripening 1 (ASR1), a sequence-specific DNA protein that has no orthologues in the Arabidopsis genome. ASR1-overexpressing (ASR1-OE) plants display an abscisic acid-insensitive 4 (abi4) phenotype: seed germination is not sensitive to inhibition by abscisic acid (ABA), glucose, NaCl and paclobutrazol. ASR1 binds coupling element 1 (CE1), a cis-acting element bound by the ABI4 transcription factor, located in the ABI4-regulated promoters, including that of the ABI4 gene. Chromatin immunoprecipitation demonstrates that ASR1 is bound in vivo to the promoter of the ABI4 gene in ASR1-OE plants, but not to promoters of genes known to be regulated by the transcription factors ABI3 or ABI5. Real-time polymerase chain reaction (PCR) analysis confirmed that the expression of ABI4 and ABI4-regulated genes is markedly reduced in ASR1-OE plants. Therefore, it is concluded that the abi4 phenotype of ASR1-OE plants is the result of competition between the foreign ASR1 and the endogenous ABI4 on specific promoter DNA sequences. The biotechnological advantage of using this approach in crop plants from the Brassicaceae family to reduce the transactivation activity of ABI4 is discussed.

Abscisic acid stress ripening 1 (ASR1) is a low molecular weight plant-specific protein encoded by an abiotic stress-regulated gene. Overexpression of ASR1 in transgenic plants increases their salt tolerance. The ASR1 protein possesses a zinc-dependent DNA-binding activity. The DNA-binding site was mapped to the central part of the polypeptide using truncated forms of the protein. Two additional zinc-binding sites were shown to be localized at the amino terminus of the polypeptide. ASR1 protein is presumed to be an intrinsically unstructured protein using a number of prediction algorithms. The degree of order of ASR1 was determined experimentally using nontagged recombinant protein expressed in Escherichia coli and purified to homogeneity. Purified ASR1 was shown to be unfolded using dynamic light scattering, gel filtration, microcalorimetry, circular dichroism, and Fourier transform infrared spectrometry. The protein was shown to be monomeric by analytical ultracentrifugation. Addition of zinc ions resulted in a global change in ASR1 structure from monomer to homodimer. Upon binding of zinc ions, the protein becomes ordered as shown by Fourier transform infrared spectrometry and microcalorimetry, concomitant with dimerization. Tomato (Solanum lycopersicum) leaf soluble ASR1 is unstructured in the absence of added zinc and gains structure upon binding of the metal ion. The effect of zinc binding on ASR1 folding and dimerization is discussed.

We have recently demonstrated that the transcription factor ABSCISIC ACID INSENSITIVE 4 (ABI4) mediates abscisic acid and cytokinin inhibition of lateral root formation by reducing polar auxin transport in Arabidopsis thaliana. ( 1) In that study, we provided a direct demonstration of ABI4 expression in phloem companion cells and parenchyma of the vascular system in the mature regions of the roots. Although also studied in mature plants, ABI4 has been studied primarily in germinating seedlings, and its expression has been assumed by some researchers to be restricted to early germination stages. We thus constructed transgenic Arabidopsis plants expressing an ABI4:GUS construct, and followed ABI4 promoter activity during seedling development, focusing on the roots.

The manipulation of transacting factors is commonly used to achieve a wide change in the expression of a large number of genes in transgenic plants as a result of a change in the expression of a single gene product. This is mostly achieved by the overexpression of transactivator or repressor proteins. In this study, it is demonstrated that the overexpression of an exogenous DNA-binding protein can be used to compete with the expression of an endogenous transcription factor sharing the same DNA-binding sequence. Arabidopsis was transformed with cDNA encoding tomato abscisic acid stress ripening 1 (ASR1), a sequence-specific DNA protein that has no orthologues in the Arabidopsis genome. ASR1-overexpressing (ASR1-OE) plants display an abscisic acid-insensitive 4 (abi4) phenotype: seed germination is not sensitive to inhibition by abscisic acid (ABA), glucose, NaCl and paclobutrazol. ASR1 binds coupling element 1 (CE1), a cis-acting element bound by the ABI4 transcription factor, located in the ABI4-regulated promoters, including that of the ABI4 gene. Chromatin immunoprecipitation demonstrates that ASR1 is bound in vivo to the promoter of the ABI4 gene in ASR1-OE plants, but not to promoters of genes known to be regulated by the transcription factors ABI3 or ABI5. Real-time polymerase chain reaction (PCR) analysis confirmed that the expression of ABI4 and ABI4-regulated genes is markedly reduced in ASR1-OE plants. Therefore, it is concluded that the abi4 phenotype of ASR1-OE plants is the result of competition between the foreign ASR1 and the endogenous ABI4 on specific promoter DNA sequences. The biotechnological advantage of using this approach in crop plants from the Brassicaceae family to reduce the transactivation activity of ABI4 is discussed.