Potent and selective inhibitors of PI3Kδ: obtaining isoform selectivity from the affinity pocket and tryptophan shelf

A potent inhibitor of PI3Kδ that is ≥ 200 fold selective for the remaining three Class I PI3K isoforms and additional kinases is described. The hypothesis for selectivity is illustrated through structure activity relationships and crystal structures of compounds bound to a K802T mutant of PI3Kγ. Pharmacokinetic data in rats and mice support the use of 3 as a useful tool compound to use for in vivo studies.     

The apoplastic oxidative burst peroxidase in Arabidopsis is a major component of pattern-triggered immunity

In plants, reactive oxygen species (ROS) associated with the response to pathogen attack are generated by NADPH oxidases or apoplastic peroxidases. Antisense expression of a heterologous French bean (Phaseolus vulgaris) peroxidase (FBP1) cDNA in Arabidopsis thaliana was previously shown to diminish the expression of two Arabidopsis peroxidases (peroxidase 33 [PRX33] and PRX34), block the oxidative burst in response to a fungal elicitor, and cause enhanced susceptibility to a broad range of fungal and bacterial pathogens. Here we show that mature leaves of T-DNA insertion lines with diminished expression of PRX33 and PRX34 exhibit reduced ROS and callose deposition in response to microbe-associated molecular patterns (MAMPs), including the synthetic peptides Flg22 and Elf26 corresponding to bacterial flagellin and elongation factor Tu, respectively. PRX33 and PRX34 knockdown lines also exhibited diminished activation of Flg22-activated genes after Flg22 treatment. These MAMP-activated genes were also downregulated in unchallenged leaves of the peroxidase knockdown lines, suggesting that a low level of apoplastic ROS production may be required to preprime basal resistance. Finally, the PRX33 knockdown line is more susceptible to Pseudomonas syringae than wild-type plants. In aggregate, these data demonstrate that the peroxidase-dependent oxidative burst plays an important role in Arabidopsis basal resistance mediated by the recognition of MAMPs.     

TAK1-TAB2 signaling contributes to bone destruction by breast carcinoma cells

Advanced-stage breast cancers frequently metastasize to the bones and cause bone destruction, but the underlying mechanism is not fully understood. This study presents evidence that TGF-β-activated protein kinase 1 (TAK1) signaling in tumor cells promotes bone destruction by metastatic breast carcinoma cells, controlling expression of prometastatic factors including matrix metalloproteinase (MMP) 9 and COX2. Suppression of TAK1 signaling by dominant-negative TAK1 (dn-TAK1) in breast carcinoma MDA-MB-231 cells impairs bone colonization by carcinoma cells and bone osteolysis in the intracardiac injection model. Mechanistic studies showed that inhibition of TAK1 by dn-TAK1 or siRNA blocked expression of factors implicated in bone metastasis, such as MMP-9, COX2/PTGS2, parathyroid hormone-related protein (PTHrP) and interleukin 8 (IL-8), but did not affect activation of p38MAPK by TGF-β. TAK1 signaling is mediated by TAK1-binding partners TAB1, TAB2, and TAB3. Carcinoma cells express elevated mRNA levels of TAB2 and TAB3, whereas the TAB1 expression is noticeably low. Accordingly, depletion of TAB2 by siRNA reduced expression of MMP-9 and COX2. Together, these studies show that the TAK1-TAB2-TAB3 signaling axis is critical for carcinoma-induced bone lesions, mediating expression of proinvasive and osteolytic factors. These findings identify the TAK1-TAB2 axis as a potential therapeutic target in bone metastasis.     

A novel high-throughput in vivo molecular screen for shade avoidance mutants identifies a novel phyA mutation

The shade avoidance syndrome (SAS) allows plants to anticipate and avoid shading by neighbouring plants by initiating an elongation growth response. The phytochrome photoreceptors are able to detect a reduction in the red:far red ratio in incident light, the result of selective absorption of red and blue wavelengths by proximal vegetation. A shade-responsive luciferase reporter line (PHYB::LUC) was used to carry out a high-throughput screen to identify novel SAS mutants. The dracula 1 (dra1) mutant, that showed no avoidance of shade for the PHYB::LUC response, was the result of a mutation in the PHYA gene. Like previously characterized phyA mutants, dra1 showed a long hypocotyl in far red light and an enhanced hypocotyl elongation response to shade. However, dra1 additionally showed a long hypocotyl in red light. Since phyB levels are relatively unaffected in dra1, this gain-of-function red light phenotype strongly suggests a disruption of phyB signalling. The dra1 mutation, G773E within the phyA PAS2 domain, occurs at a residue absolutely conserved among phyA sequences. The equivalent residue in phyB is absolutely conserved as a threonine. PAS domains are structurally conserved domains involved in molecular interaction. Structural modelling of the dra1 mutation within the phyA PAS2 domain shows some similarity with the structure of the phyB PAS2 domain, suggesting that the interference with phyB signalling may be the result of non-functional mimicry. Hence, it was hypothesized that this PAS2 residue forms a key distinction between the phyA and phyB phytochrome species.     

Applications of Molecular Markers in Fruit Crops for Breeding Programs—A Review

Selection and use of molecular markers for evaluation of DNA polymorphism in plants are couple of the most important approaches in the field of molecular genetics. The assessment of genetic diversity using morphological markers is not sufficient due to little differentiating traits among the species, genera or their individuals. Morphological markers are not only highly influenced by environmental factors but skilled assessment is also prerequisite to find the variations in plant genetic resources. Therefore, molecular markers are considered as efficient tools for detailed DNA based characterization of fruit crops. Molecular markers provide new directions to the efforts of plant breeders particularly in genetic variability, gene tags, gene localization, taxonomy, genetic diversity, phylogenetic analysis and also play an important role to decrease the time required for development of new and excellent cultivars. The success of molecular markers technology in genetic improvement programs depends on the close relationship among the plant breeders, biotechnologists, skilled manpower and good financial support. The present review describes application and success of molecular markers technology used for genetic improvement in different fruit crops.     

The Arabidopsis protein kinase PTI1-2 is activated by convergent phosphatidic acid and oxidative stress signaling pathways downstream of PDK1 and OXI1

Arabidopsis PDK1 activity is regulated by binding to the lipid phosphatidic acid (PA) resulting in activation of the oxidative stress-response protein kinase OXI1/AGC2-1. Thus there is an inferred link between lipid signaling and oxidative stress signaling modules. Among a panel of hormones and stresses tested, we found that, in addition to PA, the fungal elicitor xylanase activated PDK1, suggesting that PDK1 has a role in plant pathogen defense mechanisms. The downstream OXI1 was activated by additional stress factors, including PA, H(2)O(2), and partially by xylanase. We have isolated an interacting partner of OXI1, a Ser/Thr kinase (PTI1-2), which is downstream of OXI1. Its sequence closely resembles the tomato Pti kinase, which has been implicated in the hypersensitive response, a localized programmed cell death that occurs at the site of pathogen infection. PTI1-2 is activated by the same stresses/elicitors as OXI1 and additionally flagellin. We have used RNA interference to knock out the expression of PDK1 and OXI1 and to study the effects on PTI1-2 activity. We show that specific lipid signaling pathways converge on PTI1-2 via the PDK1-OXI1 axis, whereas H(2)O(2) and flagellin signals to OXI1-PTI1-2 via a PDK1-independent pathway. PTI1-2 represents a new downstream component that integrates diverse lipid and reactive oxygen stress signals and functions closely with OXI1.     

Pleiotropic effects on mandibular morphology I. Developmental morphological integration and differential dominance

Pleiotropy refers to a single genetic locus that affects more than one phenotypic trait. Pleiotropic effects of genetic loci are thought to play an important role in evolution, reflecting functional and developmental relationships among phenotypes. In a previous study, we examined pleiotropic effects displayed by quantitative trait loci (QTLs) on murine mandibular morphology in relation to mandibular structure and function. In replicating most of our previous QTLs and increasing our sample size, this study strengthens and extends our earlier results. As in our previous study, we find that QTL effects tend to be restricted to developmentally or functionally related traits. In addition, we examine patterns of differential dominance for pleiotropic QTL effects. Differential dominance occurs when dominance patterns for a single locus vary among traits. We find that multivariate overdominance is a common and substantial phenomenon, and may potentially provide an explanation for the persistence of heterozygosity in natural populations.