The novel cyst nematode effector protein 30D08 targets host nuclear functions to alter gene expression in feeding sites

• Cyst nematodes deliver effector proteins into host cells to manipulate cellular processes and establish a metabolically hyperactive feeding site. The novel 30D08 effector protein is produced in the dorsal gland of parasitic juveniles, but its function has remained unknown. • We demonstrate that expression of 30D08 contributes to nematode parasitism, the protein is packaged into secretory granules, and is targeted to the plant nucleus where it interacts with SMU2 (homologue of suppressor of mec-8 and unc-52 2), an auxiliary spliceosomal protein. • We show that SMU2 is expressed in feeding sites and a smu2 mutant is less susceptible to nematode infection. In Arabidopsis expressing 30D08 under the SMU2 promoter, several genes were found to be alternatively spliced and the most abundant functional classes represented among differentially expressed genes were involved in RNA processing, transcription and binding, as well as in development, hormone and secondary metabolism representing key cellular processes known to be important for feeding site formation. • In conclusion, we demonstrated that the 30D08 effector is secreted from the nematode and targeted to the plant nucleus where its interaction with a host auxiliary spliceosomal protein may alter the pre-mRNA splicing and expression of a subset of genes important for feeding site formation

Spatial distribution of transcript changes in the maize primary root elongation zone at low water potential

Background: Previous work showed that the maize primary root adapts to low Ψw (-1.6 MPa) by maintaining longitudinal expansion in the apical 3 mm (region 1), whereas in the adjacent 4 mm (region 2) longitudinal expansion reaches a maximum in well-watered roots but is progressively inhibited at low Ψw. To identify mechanisms that determine these responses to low Ψw, transcript expression was profiled in these regions of water-stressed and well-watered roots. In addition, comparison between region 2 of water-stressed roots and the zone of growth deceleration in well-watered roots (region 3) distinguished stress-responsive genes in region 2 from those involved in cell maturation. Results: Responses of gene expression to water stress in regions 1 and 2 were largely distinct. The largest functional categories of differentially expressed transcripts were reactive oxygen species and carbon metabolism in region 1, and membrane transport in region 2. Transcripts controlling sucrose hydrolysis distinguished well-watered and water-stressed states (invertase vs. sucrose synthase), and changes in expression of transcripts for starch synthesis indicated further alteration in carbon metabolism under water deficit. A role for inositols in the stress response was suggested, as was control of proline metabolism. Increased expression of transcripts for wall-loosening proteins in region 1, and for elements of ABA and ethylene signaling were also indicated in the response to water deficit. Conclusion: The analysis indicates that fundamentally different signaling and metabolic response mechanisms are involved in the response to water stress in different regions of the maize primary root elongation zone

Emerging Use of Gene Expression Microarrays in Plant Physiology

Microarrays have become an important technology for the global analysis of gene expression in humans, animals, plants, and microbes. Implemented in the context of a well-designed experiment, cDNA and oligonucleotide arrays can provide highthroughput, simultaneous analysis of transcript abundance for hundreds, if not thousands, of genes. However, despite widespread acceptance, the use of microarrays as a tool to better understand processes of interest to the plant physiologist is still being explored. To help illustrate current uses of microarrays in the plant sciences, several case studies that we believe demonstrate the emerging application of gene expression arrays in plant physiology were selected from among the many posters and presentations at the 2003 Plant and Animal Genome XI Conference. Based on this survey, microarrays are being used to assess gene expression in plants exposed to the experimental manipulation of air temperature, soil water content and aluminium concentration in the root zone. Analysis often includes characterizing transcript profiles for multiple post-treatment sampling periods and categorizing genes with common patterns of response using hierarchical clustering techniques. In addition, microarrays are also providing insights into developmental changes in gene expression associated with fibre and root elongation in cotton and maize, respectively. Technical and analytical limitations of microarrays are discussed and projects attempting to advance areas of microarray design and data analysis are highlighted. Finally, although much work remains, we conclude that microarrays are a valuable tool for the plant physiologist interested in the characterization and identification of individual genes and gene families with potential application in the fields of agriculture, horticulture and forestry

Jasmonoyl isoleucine accumulation is needed for abscisic acid build-up in roots of Arabidopsis under water stress conditions

Phytohormones are central players in sensing and signallingnumerous environmental conditions like drought. In thiswork, hormone profiling together with gene expression ofkey enzymes involved in abscisic acid (ABA) and jasmonatebiosynthesis were studied in desiccating Arabidopsis roots.Jasmonic acid (JA) content transiently increased after stressimposition whereas progressive and concomitant ABA andJasmonoyl Isoleucine (JA-Ile) accumulations were detected.Molecular data suggest that, at least, part of the hormonalregulation takes place at the biosynthetic level. These obser-vations also point to a possible involvement of jasmonates onABA biosynthesis under stress. To test this hypothesis,mutants impaired in jasmonate biosynthesis (opr3, lox6 andjar1-1) and in JA-dependent signalling (coi1) wereemployed. Results showed that the early JA accumulationleading to JA-Ile build up was necessary for an ABA increasein roots under two different water stress conditions. Signaltransduction between water stress-induced JA-Ile accumula-tion and COI1 is necessary for a full induction of the ABAbiosynthesis pathway and subsequent hormone accumula-tion in roots of Arabidopsis plants. The present work adds alevel of interaction between jasmonates and ABA at thebiosynthetic levelThis work was supported by the Spanish Ministerio deEconomía y Competitividad (MINECO) through grantsAGL2010-22195-C03-01 and AGL2013-42038R to A.G.-C.Hormonal profiles were performed at Instrumental centralfacilities (SCIC) of Universitat Jaume I. The authors have noconflict of interest to declar

Elevated cytokinin content in ipt transgenic creeping bentgrass promotes drought tolerance through regulating metabolite accumulation

Increased endogenous plant cytokinin (CK) content through transformation with an adenine isopentyl transferase (ipt) gene has been associated with improved plant drought tolerance. The objective of this study is to determine metabolic changes associated with elevated CK production in ipt transgenic creeping bentgrass (Agrostis stolonifera L.) with improved drought tolerance. Null transformants (NTs) and plants transformed with ipt controlled by a stress- or senescence-activated promoter (SAG12-ipt) were exposed to well-watered conditions or drought stress by withholding irrigation in an environmental growth chamber. Physiological analysis confirmed that the SAG12-ipt line (S41) had improved drought tolerance compared with the NT plants. Specific metabolite changes over the course of drought stress and differential accumulation of metabolites in SAG12-ipt plants compared with NT plants at the same level of leaf relative water content (47% RWC) were identified using gas chromatography–mass spectroscopy. The metabolite profiling analysis detected 45 metabolites differentially accumulated in response to ipt expression or drought stress, which included amino acids, carbohydrates, organic acids, and organic alcohols. The enhanced drought tolerance of SAG12-ipt plants was associated with the maintenance of accumulation of several metabolites, particularly amino acids (proline, γ-aminobutyric acid, alanine, and glycine) carbohydrates (sucrose, fructose, maltose, and ribose), and organic acids that are mainly involved in the citric acid cycle. The accumulation of these metabolites could contribute to improved drought tolerance due to their roles in the stress response pathways such as stress signalling, osmotic adjustment, and respiration for energy production

Cloning and functional analysis of a fructosyltransferase cDNA for synthesis of highly polymerized levans in timothy (Phleum pratense L.)

Variation in the structures of plant fructans and their degree of polymerization (DP) can be explained as the result of diverse combinations of fructosyltransferases (FTs) with different properties. Although FT genes have been isolated in a range of plant species, sucrose:fructan 6-fructosyltransferase (6-SFT) cDNAs have only been functionally characterized in a few species such as wheat. A novel FT cDNA possessing 6-SFT activity has been identified and characterized from the temperate forage grass, timothy (Phleum pratense L.). The cDNA of an FT homolog, PpFT1, was isolated from cold-acclimated timothy. A recombinant PpFT1 protein expressed in Pichia pastoris showed 6-SFT/sucrose:sucrose 1-fructosyltransferase (1-SST) activity and produced linear β(2,6)-linked levans from sucrose with higher DPs than present in graminans formed in vitro by wheat 6-SFT (Wft1). PpFT1 and Wft1 showed remarkably different acceptor substrate specificities: PpFT1 had high affinity for 6-kestotriose to produce levans and low affinity for 1-kestotriose, whereas Wft1 preferentially used 1-kestotriose as an acceptor. The affinity of the PpFT1 recombinant enzyme for sucrose as a substrate was lower than that of the Wft1 recombinant enzyme. It is also confirmed that timothy seedlings had elevated levels of PpFT1 transcripts during the accumulation of fructans under high sucrose and cold conditions. Our results suggest that PpFT1 is a novel cDNA with unique enzymatic properties that differ from those of previously cloned plant 6-SFTs, and is involved in the synthesis of highly polymerized levans in timothy

The redox state of the apoplast influences the acclimation of photosynthesis and leaf metabolism to changing irradiance

The redox state of the apoplast is largely determined by ascorbate oxidase (AO) activity. The influence of AO activity on leaf acclimation to changing irradiance was explored in wild‐type (WT) and transgenic tobacco (Nicotiana tobaccum) lines containing either high [pumpkin AO (PAO)] or low [tobacco AO (TAO)] AO activity at low [low light (LL); 250 μmol m⁻² s⁻¹] and high [high light (HL); 1600 μmol m⁻² s⁻¹] irradiance and following the transition from HL to LL. AO activities changed over the photoperiod, particularly in the PAO plants. AO activity had little effect on leaf ascorbate, which was significantly higher under HL than under LL. Apoplastic ascorbate/dehydroascorbate (DHA) ratios and threonate levels were modified by AO activity. Despite decreased levels of transcripts encoding ascorbate synthesis enzymes, leaf ascorbate increased over the first photoperiod following the transition from HL to LL, to much higher levels than LL‐grown plants. Photosynthesis rates were significantly higher in the TAO leaves than in WT or PAO plants grown under HL but not under LL. Sub‐sets of amino acids and fatty acids were lower in TAO and WT leaves than in the PAO plants under HL, and following the transition to LL. Light acclimation processes are therefore influenced by the apoplastic as well as chloroplastic redox state