BackgroundPhosphorus is one of the macronutrients essential for plant growth and development. The acquisition and translocation of phosphate are pivotal processes of plant growth. In a large number of plants, phosphate uptake by roots and translocation within the plant are presumed to occur via a phosphate/proton cotransport mechanism.Principal FindingsWe cloned two cDNAs from soybean (Glycine max), GmPT1 and GmPT2, which show homology to the phosphate/proton cotransporter PHO84 from the budding yeast Saccharomyces cerevisiae. The amino acid sequence of the products predicted from GmPT1 and GmPT2 share 61% and 63% identity, respectively, with the PHO84 in amino acid sequence. The deduced structure of the encoded proteins revealed 12 membrane-spanning domains with a central hydrophilic region. The molecular mass values are ∼58.7 kDa for GmPT1 and ∼58.6 kDa for GmPT2. Transiently expressed GFP–protein fusions provide direct evidence that the two Pi transporters are located in the plasma membrane. Uptake of radioactive orthophosphate by the yeast mutant MB192 showed that GmPT1 and GmPT2 are dependent on pH and uptake is reduced by the addition of uncouplers of oxidative phosphorylation. The K m for phosphate uptake by GmPT1 and GmPT2 is 6.65 mM and 6.63 mM, respectively. A quantitative real time RT-PCR assay indicated that these two genes are expressed in the roots and shoots of seedlings whether they are phosphate-deficient or not. Deficiency of phosphorus caused a slight change of the expression levels of GmPT1 and GmPT2.ConclusionsThe results of our experiments show that the two phosphate transporters have low affinity and the corresponding genes are constitutively expressed. Thereby, the two phosphate transporters can perform translocation of phosphate within the plant.

Forty-seven strains of H9 subtype avian influenza viruses identified by specific reverse transcription-PCR method were isolated from the chicken and duck flocks in different areas of China during the 2002 to 2009 epizootic period. Hemagglutinin (HA) genes of these strains were sequenced and analyzed with the representative strains published in GenBank. The results indicated that the HA genes of these strains and the vaccine strains displayed nucleotide homologies ranging from 91.7 to 96.6% and amino acid homologies ranging from 92.3 to 95.7%, respectively. Analysis of the mature peptide sequences of these HA genes showed that the presence of leucine at position 216 (corresponding to residue 226 in H3 numbering) indicated a preference to the binding of alpha (2-6) sialic acid receptors, which was the same as human isolates. Extra potential glycosylation sites appeared in the HA genes of most tested isolations compared with the vaccine strains. The HA cleavage sites of most of the strains were the 335PSRSSR downward arrow GLF341, but all of the strains met the characteristics of low-pathogenic avian influenza. The results of phylogenetic analysis indicated that all 47 strains and the current vaccine strains belong to the same phylogenetic lineage h9.4.2, but they had some genetic deviation in the last decade. Compared with the vaccine strains, 7 mutations were found in the antigen epitope region of the HA genes of the field strains. These results suggested that the commercial vaccine might not induce satisfactory prevention against infection of H9N2 avian influenza virus.

SUMMARY Plants deploy various immune receptors to recognize pathogen‐derived extracellular signals and subsequently activate the downstream defense response. Recently, increasing evidence indicates that the endoplasmic reticulum (ER) plays a part in the plant defense response, known as ER stress‐mediated immunity (ERSI), that halts pathogen infection. However, the mechanism for the ER stress response to signals of pathogen infection remains unclear. Here, we characterized the ER stress response regulator NAC089, which was previously reported to positively regulate programed cell death (PCD), functioning as an ERSI regulator. NAC089 translocated from the ER to the nucleus via the Golgi in response to Phytophthora capsici culture filtrate (CF), which is a mixture of pathogen‐associated molecular patterns (PAMPs). Plasma membrane localized co‐receptor BRASSINOSTEROID INSENSITIVE 1‐associated receptor kinase 1 (BAK1) was required for the CF‐mediated translocation of NAC089. The nuclear localization of NAC089, determined by the NAC domain, was essential for immune activation and PCD. Furthermore, NAC089 positively contributed to host resistance against the oomycete pathogen P. capsici and the bacteria pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. We also proved that NAC089‐mediated immunity is conserved in Nicotiana benthamiana. Together, we found that PAMP signaling induces the activation of ER stress in plants, and that NAC089 is required for ERSI and plant resistance against pathogens.

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