Transcriptional activation and localization of expression of Brassica juncea putative metal transport protein BjMTP1

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Arabidopsis miR827 mediates post‐transcriptional gene silencing of its ubiquitin E3 ligase target gene in the syncytium of the cyst nematode Heterodera schachtii to enhance susceptibility

MicroRNAs (miRNAs) are a major class of small non-coding RNAs with emerging functions in biotic and abiotic interactions. Here, we report on a new functional role of Arabidopsis miR827 and its NITROGEN LIMITATION ADAPTATION (NLA) target gene in mediating plant susceptibility to the beet cyst nematode Heterodera schachtii. Cyst nematodes are sedentary endoparasites that induce the formation of multinucleated feeding structures termed syncytia in the roots of host plants. Using promoter:GUS fusion assays we established that miR827 was activated in the initial feeding cells and this activation was maintained in the syncytium during all sedentary stages of nematode development. Meanwhile, the NLA target gene, which encodes an ubiquitin E3 ligase enzyme, was post-transcriptionally silenced in the syncytium, to permanently suppress its activity during all nematode parasitic stages. Overexpression of miR827 in Arabidopsis resulted in hyper-susceptibility to H. schachtii. In contrast, inactivation of miR827 activity through target mimicry or by overexpression a miR827-resistant cDNA of NLA produced the opposite phenotype of reduced plant susceptibility to H. schachtii. Gene expression analysis of several pathogenesis-related genes together with Agrobacterium–mediated transient expression in Nicotiana benthamiana provided strong evidence that miR827-mediated downregulation of NLA to suppress basal defense pathways. In addition, using yeast two-hybrid screens we identified several candidates of NLA-interacting proteins that are involved in a wide range of biological processes and molecular functions, including three pathogenesis-related proteins. Taken together, we conclude that nematode-activated miR827 in the syncytium is necessary to suppress immune responses in order to establish infection and cause disease

Root Suberin Forms an Extracellular Barrier That Affects Water Relations and Mineral Nutrition in Arabidopsis

Though central to our understanding of how roots perform their vital function of scavenging water and solutes from the soil, no direct genetic evidence currently exists to support the foundational model that suberin acts to form a chemical barrier limiting the extracellular, or apoplastic, transport of water and solutes in plant roots. Using the newly characterized enhanced suberin1 (esb1) mutant, we established a connection in Arabidopsis thaliana between suberin in the root and both water movement through the plant and solute accumulation in the shoot. Esb1 mutants, characterized by increased root suberin, were found to have reduced day time transpiration rates and increased water-use efficiency during their vegetative growth period. Furthermore, these changes in suberin and water transport were associated with decreases in the accumulation of Ca, Mn, and Zn and increases in the accumulation of Na, S, K, As, Se, and Mo in the shoot. Here, we present direct genetic evidence establishing that suberin in the roots plays a critical role in controlling both water and mineral ion uptake and transport to the leaves. The changes observed in the elemental accumulation in leaves are also interpreted as evidence that a significant component of the radial root transport of Ca, Mn, and Zn occurs in the apoplast.</p

Natural Variants of AtHKT1 Enhance Na(+) Accumulation in Two Wild Populations of Arabidopsis

Plants are sessile and therefore have developed mechanisms to adapt to their environment, including the soil mineral nutrient composition. Ionomics is a developing functional genomic strategy designed to rapidly identify the genes and gene networks involved in regulating how plants acquire and accumulate these mineral nutrients from the soil. Here, we report on the coupling of high-throughput elemental profiling of shoot tissue from various Arabidopsis accessions with DNA microarray-based bulk segregant analysis and reverse genetics, for the rapid identification of genes from wild populations of Arabidopsis that are involved in regulating how plants acquire and accumulate Na(+) from the soil. Elemental profiling of shoot tissue from 12 different Arabidopsis accessions revealed that two coastal populations of Arabidopsis collected from Tossa del Mar, Spain, and Tsu, Japan (Ts-1 and Tsu-1, respectively), accumulate higher shoot levels of Na(+) than do Col-0 and other accessions. We identify AtHKT1, known to encode a Na(+) transporter, as being the causal locus driving elevated shoot Na(+) in both Ts-1 and Tsu-1. Furthermore, we establish that a deletion in a tandem repeat sequence approximately 5 kb upstream of AtHKT1 is responsible for the reduced root expression of AtHKT1 observed in these accessions. Reciprocal grafting experiments establish that this loss of AtHKT1 expression in roots is responsible for elevated shoot Na(+). Interestingly, and in contrast to the hkt1–1 null mutant, under NaCl stress conditions, this novel AtHKT1 allele not only does not confer NaCl sensitivity but also cosegregates with elevated NaCl tolerance. We also present all our elemental profiling data in a new open access ionomics database, the Purdue Ionomics Information Management System (PiiMS; http://www.purdue.edu/dp/ionomics). Using DNA microarray-based genotyping has allowed us to rapidly identify AtHKT1 as the casual locus driving the natural variation in shoot Na(+) accumulation we observed in Ts-1 and Tsu-1. Such an approach overcomes the limitations imposed by a lack of established genetic markers in most Arabidopsis accessions and opens up a vast and tractable source of natural variation for the identification of gene function not only in ionomics but also in many other biological processes

Variation in Molybdenum Content Across Broadly Distributed Populations of Arabidopsis thaliana Is Controlled by a Mitochondrial Molybdenum Transporter (MOT1)

Molybdenum (Mo) is an essential micronutrient for plants, serving as a cofactor for enzymes involved in nitrate assimilation, sulfite detoxification, abscisic acid biosynthesis, and purine degradation. Here we show that natural variation in shoot Mo content across 92 Arabidopsis thaliana accessions is controlled by variation in a mitochondrially localized transporter (Molybdenum Transporter 1 - MOT1) that belongs to the sulfate transporter superfamily. A deletion in the MOT1 promoter is strongly associated with low shoot Mo, occurring in seven of the accessions with the lowest shoot content of Mo. Consistent with the low Mo phenotype, MOT1 expression in low Mo accessions is reduced. Reciprocal grafting experiments demonstrate that the roots of Ler-0 are responsible for the low Mo accumulation in shoot, and GUS localization demonstrates that MOT1 is expressed strongly in the roots. MOT1 contains an N-terminal mitochondrial targeting sequence and expression of MOT1 tagged with GFP in protoplasts and transgenic plants, establishing the mitochondrial localization of this protein. Furthermore, expression of MOT1 specifically enhances Mo accumulation in yeast by 5-fold, consistent with MOT1 functioning as a molybdate transporter. This work provides the first molecular insight into the processes that regulate Mo accumulation in plants and shows that novel loci can be detected by association mapping

Root Suberin Forms an Extracellular Barrier That Affects Water Relations and Mineral Nutrition in Arabidopsis

Though central to our understanding of how roots perform their vital function of scavenging water and solutes from the soil, no direct genetic evidence currently exists to support the foundational model that suberin acts to form a chemical barrier limiting the extracellular, or apoplastic, transport of water and solutes in plant roots. Using the newly characterized enhanced suberin1 (esb1) mutant, we established a connection in Arabidopsis thaliana between suberin in the root and both water movement through the plant and solute accumulation in the shoot. Esb1 mutants, characterized by increased root suberin, were found to have reduced day time transpiration rates and increased water-use efficiency during their vegetative growth period. Furthermore, these changes in suberin and water transport were associated with decreases in the accumulation of Ca, Mn, and Zn and increases in the accumulation of Na, S, K, As, Se, and Mo in the shoot. Here, we present direct genetic evidence establishing that suberin in the roots plays a critical role in controlling both water and mineral ion uptake and transport to the leaves. The changes observed in the elemental accumulation in leaves are also interpreted as evidence that a significant component of the radial root transport of Ca, Mn, and Zn occurs in the apoplast

Virus -host interactions in alfalfa mosaic virus-Arabidopsis thaliana pathosystem

Hosts amenable to studies at the molecular level are currently not available to identify host genes involved in AMV infection. So, we identified and characterized Arabidopsis as a host for AMV. Sixty five ecotypes supported AMV infection, while 3 could not be infected. However, none of the susceptible ecotypes displayed any characteristic symptoms. AMV infection in Col-0 ecotype, which supported vigorous systemic infection and accumulated higher levels of AMV than in the symptomatic host Nicotiana tabacum, was further characterized by using infectivity assays, electron microscopy, and protoplast assays. Using two hybrid assays, candidate Arabidopsis proteins that interacted with AMV coat protein were identified. Some of the putative interacting partners have been implicated in other virus infections and hence constitute primary candidates for confirmation in in vitro and in planta pull-down assays. To do that, we developed many tools including affinity-tagged recombinant proteins and antibodies. One candidate CP-host protein interaction was also demonstrated in vitro by using pull-down assays. Yeast two-hybrid assays also identified one Arabidopsis protein that interacted with the methyltransferase domain of the AMV P1 protein

Synchronization of chaotic systems using feedback controller: An application to Diffie–Hellman key exchange protocol and ElGamal public key cryptosystem

In this paper, designing an appropriate linear and nonlinear feedback control, the two identical integer order chaotic systems are synchronized by analytically and numerically. It has been realizing that, synchronization using linear feedback control method is efficient than nonlinear feedback control method due to the less computational complexity and the synchronization error. ElGamal public key cryptosystem is described through the proposed Diffie–Hellman key exchange protocol based on the synchronized chaotic systems using linear feedback control and their security are analyzed. The numerical simulations are given to validate the correctness of the proposed synchronization of chaotic systems and the ElGamal cryptosystem

Sliding mode control for generalized robust synchronization of mismatched fractional order dynamical systems and its application to secure transmission of voice messages

This paper proposes a generalized robust synchronization method for different dimensional fractional order dynamical systems with mismatched fractional derivatives in the presence of function uncertainty and external disturbance by a designing sliding mode controller. Based on the proposed theory of generalized robust synchronization criterion, a novel audio cryptosystem is proposed for sending or sharing voice messages secretly via insecure channel. Numerical examples are given to verify the potency of the proposed theories