Phenotypes Conferred by Wheat Multiple Pathogen Resistance Locus, , Include Cell Death in Response to Biotic and Abiotic Stresses.

The wheat locus confers partial resistance to four biotrophic pathogens: wheat stem rust ( f. sp. ), leaf rust (), stripe rust ( f.

Cellular and molecular characterization of a stem rust resistance locus on wheat chromosome 7AL.

Background: Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is a major wheat disease which is mainly controlled through the release of resistant cultivars containing one or several resistance genes.

Identification of a stem rust resistance locus effective against Ug99 on wheat chromosome 7AL using a RAD-Seq approach.

A locus of major effect for stem rust resistance, effective against Ug99 and possibly a target of a suppressor on chromosome arm 7DL in wheat cultivar Canthatch, was mapped to 7AL. Wheat stem rust, caused by Puccinia graminis f. sp.

Specificity of a Rust Resistance Suppressor on 7DL in the Spring Wheat Cultivar Canthatch.

The spring wheat 'Canthatch' has been shown to suppress stem rust resistance genes in the background due to the presence of a suppressor gene located on the long arm of chromosome 7D. However, it is unclear whether the suppressor also suppresses resistance genes against leaf rust and stripe rust. In this study, we investigated the specificity of the resistance suppression.

Major haplotype divergence including multiple germin-like protein genes, at the wheat Sr2 adult plant stem rust resistance locus.

Background: The adult plant stem rust resistance gene Sr2 was introgressed into hexaploid wheat cultivar (cv) Marquis from tetraploid emmer wheat cv Yaroslav, to generate stem rust resistant cv Hope in the 1920s. Subsequently, Sr2 has been widely deployed and has provided durable partial resistance to all known races of Puccinia graminis f. sp.

A multiple resistance locus on chromosome arm 3BS in wheat confers resistance to stem rust (Sr2), leaf rust (Lr27) and powdery mildew.

Sr2 is the only known durable, race non-specific adult plant stem rust resistance gene in wheat. The Sr2 gene was shown to be tightly linked to the leaf rust resistance gene Lr27 and to powdery mildew resistance. An analysis of recombinants and mutants suggests that a single gene on chromosome arm 3BS may be responsible for resistance to these three fungal pathogens.

Overexpression of serine acetlytransferase produced large increases in O-acetylserine and free cysteine in developing seeds of a grain legume.

There have been many attempts to increase concentrations of the nutritionally essential sulphur amino acids by modifying their biosynthetic pathway in leaves of transgenic plants. This report describes the first modification of cysteine biosynthesis in developing seeds; those of the grain legume, narrow leaf lupin (Lupinus angustifolius, L.).

Starch storage in the stems of wheat plants: localization and temporal changes.

Background And Aims: Carbohydrate temporarily accumulates in wheat stems during the early reproductive growth phase, predominantly as water soluble carbohydrate (WSC), and is subsequently remobilized during grain filling. Starch has also been reported as a minor storage carbohydrate component in wheat stems, but the details are lacking.

Methods: The accumulation and localization of starch in wheat stem and leaf sheath tissue over a developmental period from 6 d before anthesis to 35 d after anthesis was investigated.

Large scale transcriptome analysis of the effects of nitrogen nutrition on accumulation of stem carbohydrate reserves in reproductive stage wheat.

We investigated the molecular basis of the long-term adaptation to nitrogen (N) limitation of wheat plants grown in a simulated crop canopy, with a focus on the stage when carbon (C) reserves are accumulated in stems for later remobilization to grain. A cDNA microarray representing approximately 36,000 unique sequences was used to compare gene expression in a number of above-ground organs at anthesis. Fructan accumulation in stems was accompanied by elevated transcripts for a suite of fructosyltransferases (FTs) and for a fructan 6-exohydrolase (6-FEH) in the low N compared to high N stems.

Genetic contributions to agricultural sustainability.

The current tools of enquiry into the structure and operation of the plant genome have provided us with an understanding of plant development and function far beyond the state of knowledge that we had previously. We know about key genetic controls repressing or stimulating the cascades of gene expression that move a plant through stages in its life cycle, facilitating the morphogenesis of vegetative and reproductive tissues and organs. The new technologies are enabling the identification of key gene activity responses to the range of biotic and abiotic challenges experienced by plants.

Genotypic variation in water-soluble carbohydrate accumulation in wheat.

The water-soluble carbohydrate (WSC) that accumulates in the stems of wheat during growth can be an important contributor to grain filling, particularly under conditions when assimilation is limited, such as during end-of-season drought. WSC concentration was measured at anthesis across a diverse set of wheat genotypes over multiple environments. Environmental differences in WSC concentration were large (means for the set ranging between 108 and 203 mg g dry weight), and there were significant and repeatable differences in WSC accumulation among genotypes (means ranging from 112 to 213 mg g dry weight averaged across environments), associated with large broad-sense heritability (H = 0.

Sulphur and nitrogen nutrition influence the response of chickpea seeds to an added, transgenic sink for organic sulphur.

In order to increase the concentration of the nutritionally essential sulphur amino acids in seed protein, a transgene encoding a methionine- and cysteine-rich protein, sunflower seed albumin (SSA), was transferred to chickpeas (Cicer arietinum L). Transgenic seeds that accumulated SSA contained more methionine and less oxidized sulphur than the controls, suggesting that additional demand for sulphur amino acids from the expression of the transgene stimulated sulphur assimilation. In addition, the activity of trypsin inhibitors, a known family of endogenous, sulphur-rich chickpea seed proteins, was diminished in transgenic, SSA-containing seeds compared with the non-transgenic controls.

The redistribution of protein sulfur in transgenic rice expressing a gene for a foreign, sulfur-rich protein.

Sulfur amino acid composition is an important determinant of seed protein quality. A chimeric gene encoding sunflower seed albumin (SSA), one of the most sulfur-rich seed storage proteins identified so far, was introduced into rice (Oryza sativa) in order to modify cysteine and methionine content of the seed. Analysis of a transgenic line expressing SSA at approximately 7% of total seed protein revealed that the mature grain showed little change in the total sulfur amino acid content compared to the parental genotype.

Plasticity of seed protein composition in response to nitrogen and sulfur availability.

Seed composition is genetically programmed, but the implementation of that program is affected by many factors including the nutrition of the parent plant. In particular, seeds demonstrate a remarkable capacity to maintain nitrogen homeostasis in conditions of varying sulfur supply. They do this by altering the expression of individual genes encoding abundant storage proteins.

Limits to sulfur accumulation in transgenic lupin seeds expressing a foreign sulfur-rich protein.

The low sulfur amino acid content of legume seeds restricts their nutritive value for animals. We have investigated the limitations to the accumulation of sulfur amino acids in the storage proteins of narrow leaf lupin (Lupinus angustifolius) seeds. Variation in sulfur supply to lupin plants affected the sulfur amino acid accumulation in the mature seed.

Sulfur assimilation in developing lupin cotyledons could contribute significantly to the accumulation of organic sulfur reserves in the seed.

It is currently assumed that the assimilation of sulfur into reduced forms occurs predominantly in the leaves of plants. However, developing seeds have a strong requirement for sulfur amino acids for storage protein synthesis. We have assessed the capacity of developing seeds of narrow-leaf lupin (Lupinus angustifolius) for sulfur assimilation.

Transgenic Trifolium repens with foliage accumulating the high sulphur protein, sunflower seed albumin.

With the aim of increasing the rumen-protected level of the sulphur amino acids cysteine and methionine in Trifolium repens, we introduced the coding sequence of the sunflower seed albumin (SSA) into T. repens by Agrobacterium tumefaciens-mediated transformation. The SSA gene was modified such that the protein would be localised to the endoplasmic reticulum (ER).

Expression of the insecticidal bean alpha-amylase inhibitor transgene has minimal detrimental effect on the nutritional value of peas fed to rats at 30% of the diet.

The effect of expression of bean alpha-amylase inhibitor (alpha-AI) transgene on the nutritional value of peas has been evaluated by pair-feeding rats diets containing transgenic or parent peas at 300 and 650 g/kg, respectively, and at 150 g protein/kg diet, supplemented with essential amino acids to target requirements. The results were also compared with the effects of diets containing lactalbumin with or without 0.9 or 2.

The influences of two plant nuclear matrix attachment regions (MARs) on gene expression in transgenic plants.

Nuclear matrix attachment regions (MARs) are thought to influence gene expression by anchoring active chromatin to the proteinaceous nuclear matrix. In this study, two plant DNA fragments with strong MAR activity were selected and tested for their effects on expression of a linked reporter gene in transgenic tobacco. One MAR was isolated from the 5' flanking region of a pea vicilin gene previously reported to be expressed in a copy number-dependent manner in transgenic tobacco.

Enhanced methionine levels and increased nutritive value of seeds of transgenic lupins (Lupinus angustifolius L.) expressing a sunflower seed albumin gene.

With the aim of improving the nutritive value of an important grain legume crop, a chimeric gene specifying seed-specific expression of a sulfur-rich, sunflower seed albumin was stably transformed into narrow-leafed lupin (Lupinus angustifolius L.). Sunflower seed albumin accounted for 5% of extractable seed protein in a line containing a single tandem insertion of the transferred DNA.

Accumulation of a sulphur-rich seed albumin from sunflower in the leaves of transgenic subterranean clover (Trifolium subterraneum L.).

A gene encoding a sulphur-rich, sunflower seed albumin (23% cysteine plus methionine) was modified to contain the promoter for the 35S RNA of cauliflower mosaic virus, in order to obtain leaf expression in transgenic plants. In addition, a sequence encoding an endoplasmic reticulum-retention signal was added to the 3' end of the coding region so as to stabilize the protein by diverting it away from the vacuole. The modified gene was introduced into subterranean clover (T.

A biotechnological approach to improving the nutritive value of alfalfa.

The postruminal supply of the sulfur-containing amino acids, methionine and cysteine, has been reported to be a major limitation to wool growth in sheep. We aim to improve the protein quality of forage for ruminants by introducing into alfalfa chimeric genes encoding a ruminally stable, sulfur amino acid-rich protein from sunflower seeds. Four gene constructs were transferred to Australian commercial cultivars of alfalfa using Agrobacterium tumefaciens-mediated transformation and selection with phosphinothricin (PPT).

Bean [alpha]-Amylase Inhibitor Confers Resistance to the Pea Weevil (Bruchus pisorum) in Transgenic Peas (Pisum sativum L.).

Bruchid larvae cause major losses of grain legume crops through-out the world. Some bruchid species, such as the cowpea weevil and the azuki bean weevil, are pests that damage stored seeds. Others, such as the pea weevil (Bruchus pisorum), attack the crop growing in the field.

Agrobacterium-Mediated Transformation of Subterranean Clover (Trifolium subterraneum L.).

We have developed a rapid and reproducible transformation system for subterranean clover (Trifolium subterraneum L.) using Agrobacterium tumefaciens-mediated gene delivery. Hypocotyl segments from seeds that had been allowed to imbibe were used as explants, and regeneration was achieved via organogenesis.

Genetic engineering of grain and pasture legumes for improved nutritive value.

This review describes work aimed at the improvement of the nutritive value of grain and forage legumes using gene transfer techniques. Two traits which are amenable to manipulation by genetic engineering have been identified. These are plant protein quality and lignin content.