抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Summary The Agrobacterium vacuum infiltration method has made it possible to transform Arabidopsis thaliana without plant tissue culture or regeneration. In the present study, this method was evaluated and a substantially modified transformation method was developed. The labor-intensive vacuum infiltration process was eliminated in favor of simple dipping of developing floral tissues into a solution containing Agrobacterium tumefaciens, 5% sucrose and 500 microliters per litre of surfactant Silwet L-77. Sucrose and surfactant were critical to the success of the floral dip method. Plants inoculated when numerous immature floral buds and few siliques were present produced transformed progeny at the highest rate. Plant tissue culture media, the hormone benzylamino purine and pH adjustment were unnecessary, and Agrobacterium could be applied to plants at a range of cell densities. Repeated application of Agrobacterium improved transformation rates and overall yield of transformants approximately twofold. Covering plants for 1 day to retain humidity after inoculation also raised transformation rates twofold. Multiple ecotypes were transformable by this method. The modified method should facilitate high-throughput transformation of Arabidopsis for efforts such as T-DNA

/pdf/floral-dip-a-simplified-method-for-agrobacterium-mediated-4anwrgidds.pdf

Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana

The physiological and molecular mechanisms of tolerance to osmotic and ionic components of salinity stress are reviewed at the cellular, organ, and whole-plant level. Plant growth responds to salinity in two phases: a rapid, osmotic phase that inhibits growth of young leaves, and a slower, ionic phase that accelerates senescence of mature leaves. Plant adaptations to salinity are of three distinct types: osmotic stress tolerance, Na + or Cl − exclusion, and the tolerance of tissue to accumulated Na + or Cl − . Our understanding of the role of the HKT gene family in Na + exclusion from leaves is increasing, as is the understanding of the molecular bases for many other transport processes at the cellular level. However, we have a limited molecular understanding of the overall control of Na + accumulation and of osmotic stress tolerance at the whole-plant level. Molecular genetics and functional genomics provide a new opportunity to synthesize molecular and physiological knowledge to improve the salinity tolerance of plants relevant to food production and environmental sustainability.

https://rodas5.us.es/file/c2a700e9-8b4a-1970-d343-4a269c302970/1/estres_salino_bibliografia_scorm.zip/files/estres_salino_bibliografia.pdf

Mechanisms of salinity tolerance

The flowering plant Arabidopsis thaliana is an important model system for identifying genes and determining their functions. Here we report the analysis of the genomic sequence of Arabidopsis. The sequenced regions cover 115.4 megabases of the 125-megabase genome and extend into centromeric regions. The evolution of Arabidopsis involved a whole-genome duplication, followed by subsequent gene loss and extensive local gene duplications, giving rise to a dynamic genome enriched by lateral gene transfer from a cyanobacterial-like ancestor of the plastid. The genome contains 25,498 genes encoding proteins from 11,000 families, similar to the functional diversity of Drosophila and Caenorhabditis elegans--the other sequenced multicellular eukaryotes. Arabidopsis has many families of new proteins but also lacks several common protein families, indicating that the sets of common proteins have undergone differential expansion and contraction in the three multicellular eukaryotes. This is the first complete genome sequence of a plant and provides the foundations for more comprehensive comparison of conserved processes in all eukaryotes, identifying a wide range of plant-specific gene functions and establishing rapid systematic ways to identify genes for crop improvement.

/pdf/analysis-of-the-genome-sequence-of-the-flowering-plant-3vizsb52m2.pdf

Analysis of the genome sequence of the flowering plant Arabidopsis thaliana.

Demand has never been greater for revolutionary technologies that deliver fast, inexpensive and accurate genome information. This challenge has catalysed the development of next-generation sequencing (NGS) technologies. The inexpensive production of large volumes of sequence data is the primary advantage over conventional methods. Here, I present a technical review of template preparation, sequencing and imaging, genome alignment and assembly approaches, and recent advances in current and near-term commercially available NGS instruments. I also outline the broad range of applications for NGS technologies, in addition to providing guidelines for platform selection to address biological questions of interest.

/pdf/sequencing-technologies-the-next-generation-599pyrfdla.pdf

Sequencing technologies-the next generation

A method is disclosed for the direct synthesis of double stranded DNA molecules of a variety of sizes and with any desired sequence. The DNA molecule to be synthesis is logically broken up into smaller overlapping DNA segments. A maskless microarray synthesizer is used to make a DNA microarray on a substrate in which each element or feature of the array is populated by DNA of a one of the overlapping DNA segments. The DNA segments are released from the substrate and held under conditions favoring hybridization of DNA, under which conditions the segments will spontaneously hybridize together to form the desired DNA construct. This method makes possible the remote assembly of DNA sequence, through a process analogous to facsimile transmission of documents, since the information on DNA to be made can be transmitted remotely to an instrument which can then synthesize any needed DNA sequence from the information.

Method for the synthesis of dna sequences

The plasma membrane proton pump (H+-ATPase) found in plants and fungi is a P-type ATPase with a polypeptide sequence, structure, and in vivo function similar to the mammalian sodium pump (Na+, K+-ATPase). Despite its hypothetical importance for generating and maintaining the proton motive force that energizes the carriers and channels that underlie plant nutrition, genetic evidence for such a central function has not yet been reported. Using a reverse genetic approach for investigating each of the 11 isoforms in the Arabidopsis H+-ATPase (AHA) gene family, we found that one member, AHA3, is essential for pollen formation. A causative role for AHA3 in male gametogenesis was proven by complementation with a normal transgenic gene and rescue of the mutant phenotype back to wild type. We also investigated the requirement for phosphorylation of the penultimate threonine, which is found in most members of the AHA family and is thought to be involved in regulating catalytic activity. We demonstrated that a T948D mutant form of the AHA3 gene rescues the mutant phenotype in knockout AHA3 plants, but T948A does not, providing the first in planta evidence in support of the model in which phosphorylation of this amino acid is essential.

https://www.genetics.org/content/genetics/168/3/1677.full.pdf

An Arabidopsis thaliana plasma membrane proton pump is essential for pollen development.

Abscisic acid (ABA), a sesquiterpenoid phytohormone, was first discovered in the 1960s, and has since been found to be a key regulator of such diverse processes as dormancy, germination, seed development, and responses to biotic and abiotic stress (Cutler et al., 2010). Since the discovery of its structure, advances have been made in understanding ABA metabolism, synthesis, and hormone-responsive genes; however, the understanding of the early stage of ABA perception by the plant cell remained a mystery. During the past decade receptor proteins for the other traditional plant hormones (auxin, gibberellins, cytokinin, and ethylene) were discovered, while the identity of the ABA receptor remained elusive, creating controversy. Finally, in 2009, two research groups converged upon the PYR/PYL/RCAR family of soluble proteins in Arabidopsis (Arabidopsis thaliana), which evidence indicates are one type of ABA-binding receptor-like proteins (Ma et al., 2009; Park et al., 2009). This protein family has 14 members, almost all of which appear capable of forming an ABA-receptor complex that is able to activate the transcription of ABA-responsive genes. The use of multiple biochemical, chemical genetics, and proteomic approaches has provided the evidence to paint a remarkable picture of ABA binding, receptor complex formation, and initial downstream signaling. While the receptors and some important signal mediators have been elucidated, the molecular mechanisms by which they regulate the ABA signaling pathway continue to intrigue researchers and drive the field forward.

/pdf/abscisic-acid-receptors-5552kjbj1z.pdf

Abscisic acid receptors.

https://link.springer.com/content/pdf/10.1016%2Fj.jasms.2003.12.019.pdf

An isotope labeling strategy for quantifying the degree of phosphorylation at multiple sites in proteins.

A full-length cDNA encoding a calcium-dependent protein kinase with a calmodulin-like domain from Arabidopsis thaliana (AK-1 for Arabidopsis kinase-1) has been expressed as a fusion protein (called AK-1-6H) in Escherichia coli and purified to near homogeneity with high specific activity (typically 2000 nmol min-1 mg-1) using an "affinity sandwich" technique. AK-1-6H protein phosphorylation activity using histone as substrate was stimulated up to 50-fold by the addition of calcium alone or up to 5-fold by the addition of specific phospholipids alone; together calcium and these lipids acted synergistically to give up to 100-fold stimulation. We earlier reported that, of a wide array of lipids tested, only phosphatidylinositol and lysophosphatidylcholine stimulated histone phosphorylation by AK-1 [Harper, J. F., Binder, B. M., & Sussman M. R. (1993) Biochemistry 32, 3282-3290]. The properties of lipid stimulation were further explored by testing the effects of lipids on autophosphorylation and on other catalytic properties of the kinase. Although phosphatidylinositol stimulated autophosphorylation up to 11-fold, lysophosphatidylcholine was inactive. Basic peptides such as polylysine (average M(r) approximately 37,100) were potent, mixed-type inhibitors of AK-1-6H with an IC50 of 2 nM. In the presence of phosphatidylinositol, the inhibition was reduced and the IC50 for polylysine was increased to 341 nM. As with autophosphorylation, lysophosphatidylcholine was inactive in alleviating the basic peptide inhibition, which suggests that this lipid's stimulatory effects using exogenous substrate are distinct from those of phosphatidylinositol. These results are consistent with a model in which phosphoinositides directly interact with the kinase protein and alleviate a catalytic block caused by basic charges.

Michael R. Sussman

Papers

Method for the synthesis of dna sequences

An Arabidopsis thaliana plasma membrane proton pump is essential for pollen development.

Abscisic acid receptors.

An isotope labeling strategy for quantifying the degree of phosphorylation at multiple sites in proteins.

Characterization of an Arabidopsis calmodulin-like domain protein kinase purified from Escherichia coli using an affinity sandwich technique.