Light-induced expression of ipt from Agrobacterium tumefaciens results in cytokinin accumulation and osmotic stress symptoms in transgenic tobacco

Cytokinins are plant growth regulators that induce shoot formation, inhibit senescence and root growth. Experiments with hydroponically grown tobacco plants, however, indicated that exogenously applied cytokinin led to the accumulation of proline and osmotin. These responses were also associated with environmental stress reactions, such as salt stress, in many plant species. To test whether increased endogenous cytokinin accumulation led to NaCl stress symptoms, the gene ipt from Agrobacterium tumefaciens , encoding isopentenyl transferase, was transformed into Nicotiana tabacum cv. SR-1 under the control of the light-inducible rbcS-3A promoter from pea. In high light (300 μmol PPFD m -2 s -1 ), ipt mRNA was detected and zeatin/zeatin glucoside levels were 10-fold higher than in control plants or when transformants were grown in low light (30 μmol PPFD m -2 s -1 ). High light treatment was accompanied by increased levels of proline and osmotin when compared to low light grown transformed and untransformed control plants. Elevated in planta cytokinin levels induced responses also stimulated by salt stress, suggesting either common or overlapping signaling pathways are initiated independently by cytokinin and NaCl, setting in motion gene expression normally elicited by developmental processes such as flowering or environmental stress.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43438/1/11103_2004_Article_BF00020179.pd

Root-targeted biotechnology to mediate hormonal signaling and improve crop stress tolerance

peer reviewe

Genetic architecture of common bunt resistance in winter wheat using genome-wide association study

Background: Common bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA. Despite the fact that it can be easily controlled using seed treatment with fungicides, fungicides often cannot or may not be used in organic and low-input fields. Planting common bunt resistant genotypes is an alternative. Results: To identify resistance genes for Nebraska common bunt race, the global set of differential lines were inoculated. Nine differential lines carrying nine different genes had 0% infected heads and seemed to be resistant to Nebraska race. To understand the genetic basis of the resistance in Nebraska winter wheat, a set of 330 genotypes were inoculated and evaluated under field conditions in two locations. Out of the 330 genotypes, 62 genotypes had different degrees of resistance. Moreover, plant height, chlorophyll content and days to heading were scored in both locations. Using genome-wide association study, 123 SNPs located on fourteen chromosomes were identified to be associated with the resistance. Different degrees of linkage disequilibrium was found among the significant SNPs and they explained 1.00 to 9.00% of the phenotypic variance, indicating the presence of many minor QTLs controlling the resistance. Conclusion: Based on the chromosomal location of some of the known genes, some SNPs may be associated with Bt1, Bt6, Bt11 and Bt12 resistance loci. The remaining significant SNPs may be novel alleles that were not reported previously. Common bunt resistance seems to be an independent trait as no correlation was found between a number of infected heads and chlorophyll content, days to heading or plant height

MOLECULAR TECHNOLOGY FOR DEVELOPING DURABLE RESISTANCE TO THE SUGAR BEET ROOT MAGGOT (TETANOPS MYOPAEFORMIS)

Abstract Sugar beet root maggot (SBRM), Tetanops myopaeformis von Röder, is a major economic insect pest of sugar beet in North America. While several moderately resistant breeding lines have recently been registered, they do not offer complete control. A significant amount of knowledge about how plants protect themselves against insect invasion is being provided by advances being made in bioinformatics and functional genomics, however, complementary molecular studies on insect adaptive mechanisms used to overcome host resistance and develop tolerance to many insecticides are lacking. This study was initiated to establish a transcriptomic profile of SBRM genes and to identify physiologically valuable genes that can serve as targets for bio-insecticides and RNA interference mediated pest control. PCRselect suppressive subtractive hybridization (SSH) was used to produce an annotated SBRM EST dataset as a reference point for genes whose expression is modulated by interactions with resistant or susceptible sugar beet roots. This data will provide new insights into the molecular response elicited by SBRM in interactions with sugar beet roots and will advance the development of novel approaches for more effective SBRM control. Introduction Little information is available on how insects evolve adaptive mechanisms to overcome host resistance and develop tolerance to many insecticides used for their control. To gain a better understanding of insect biochemistry and molecular biology, this study was initiated to establish a transcriptomic profile of the sugar beet root maggot (SBRM, Tetanops myopaeformis) and to identify physiologically valuable genes that could serve as targets for development of pest control strategies. PCR-select suppressive subtractive hybridization (SSH) was used to generate cDNA libraries of SBRM genes that were specifically up-or down-regulated when the insect was feeding on resistant or susceptible sugar beet root

Inhibition of cysteine and aspartyl proteinases in the alfalfa weevil midgut with biochemical and plant-derived proteinase inhibitors

Proteolytic activities in alfalfa weevil (Hypera postica) larval midguts have been characterized. Effects of pH, thiol activators, low-molecular weight inhibitors, and proteinase inhibitors (PIs) on general substrate hydrolysis by midgut extracts were determined. Hemoglobinolytic activity was highest in the acidic to mildly acidic pH range, but was maximal at pH 3.5. Addition of thiolactivators dithiothreitol (DTT), 2-mercaptoethanol (2-ME), or l-cysteine had little effect on hemoglobin hydrolysis at pH 3.5, but enhanced azocaseinolytic activity two to three-fold at pH 5.0. The broad cysteine PI E-64 reduced azocaseinolytic activity by 64% or 42% at pH 5 in the presence or absence of 5 mM l-cysteine, respectively. Inhibition by diazomethyl ketones, Z-Phe–Phe–CHN2 and Z-Phe–Ala–CHN2, suggest that cathepsins L and B are present and comprise approximately 70% and 30% of the cysteine proteolytic activity, respectively. An aspartyl proteinase component was identified using pepstatin A, which inhibited 32% (pH 3.5, hemoglobin) and 50% (pH 5, azocasein) of total proteolytic activity. This activity was completely inhibited by an aspartyl proteinase inhibitor from potato (API), and is consistent with the action of a cathepsin D-like enzyme. Hence, genes encoding PIs with specificity toward cathepsins L, B and D could potentially be effective for control of alfalfa weevil using transgenic plants