Genes responding to water deficit in apple (Malus × domestica Borkh.) roots.

BACKGROUND: Individual plants adapt to their immediate environment using a combination of biochemical, morphological and life cycle strategies. Because woody plants are long-lived perennials, they cannot rely on annual life cycle strategies alone to survive abiotic stresses. In this study we used suppression subtractive hybridization to identify genes both up- and down-regulated in roots during water deficit treatment and recovery. In addition we followed the expression of select genes in the roots, leaves, bark and xylem of 'Royal Gala' apple subjected to a simulated drought and subsequent recovery. RESULTS: In agreement with studies from both herbaceous and woody plants, a number of common drought-responsive genes were identified, as well as a few not previously reported. Three genes were selected for more in depth analysis: a high affinity nitrate transporter (MdNRT2.4), a mitochondrial outer membrane translocase (MdTOM7.1), and a gene encoding an NPR1 homolog (MpNPR1-2). Quantitative expression of these genes in apple roots, bark and leaves was consistent with their roles in nutrition and defense. CONCLUSIONS: Additional genes from apple roots responding to drought were identified using suppression subtraction hybridization compared to a previous EST analysis from the same organ. Genes up- and down-regulated during drought recovery in roots were also identified. Elevated levels of a high affinity nitrate transporter were found in roots suggesting that nitrogen uptake shifted from low affinity transport due to the predicted reduction in nitrate concentration in drought-treated roots. Suppression of a NPR1 gene in leaves of drought-treated apple trees may explain in part the increased disease susceptibility of trees subjected to dehydrative conditions.

Association between oral nutritional supplementation and clinical outcomes among patients with ESRD.

BACKGROUND AND OBJECTIVES: Oral nutritional supplementation (ONS) was provided to ESRD patients with hypoalbuminemia as part of Fresenius Medical Care Health Plan's (FMCHP) disease management. This study evaluated the association between FMCHP's ONS program and clinical outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Analyses included FMCHP patients with ONS indication (n=470) defined as 2-month mean albumin <3.8 g/dl until reaching a 3-month mean ≥3.8 g/dl from February 1, 2006 to December 31, 2008. Patients did not receive ONS if deemed inappropriate or refused. Patients on ONS were compared with patients who were not, despite meeting ONS indication. Patients with ONS indication regardless of use were compared with Medicare patients with similar serum albumin levels from the 2007 Centers for Medicare and Medicaid Services Clinical Performance Measures Project (CPM). Cox models calculated adjusted hospitalization and mortality risks at 1 year. RESULTS: Among patients with indication for ONS, 276 received supplements and 194 did not. ONS use was associated with 0.058 g/dl higher serum albumin overall (P=0.02); this difference decreased by 0.001 g/dl each month (P=0.05) such that the difference was 0.052 g/dl (P=0.04) in month 6 and the difference was no longer significant in month 12 . In analyses based on ONS use, ONS patients had lower hospitalization at 1 year (68.4%; P<0.01) versus patients without ONS (88.7%), but there was no significant reduction in mortality risk (P=0.29). In analyses based on ONS indication, patients with indication had lower mortality at 1 year (16.2%) compared with CPM patients (23.4%; P<0.01). CONCLUSIONS: These findings suggest that ONS use was associated with significantly lower hospitalization rates but had no significant effect on mortality in a disease management setting.

Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus x domestica) with Erwinia amylovora.

BACKGROUND: The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceae species, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora. RESULTS: cDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized. CONCLUSION: These data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering.

Comparative expression and transcript initiation of three peach dehydrin genes.

Dehydrin genes encode proteins with demonstrated cryoprotective and antifreeze activity, and they respond to a variety of abiotic stress conditions that have dehydration as a common component. Two dehydrins from peach (Prunus persica L. [Batsch.]) have been previously characterized; here, we describe the characterization of a third dehydrin from peach bark, PpDhn3, isolated by its response to low temperature. The expression of all three dehydrin genes was profiled by semi-quantitative reverse transcription PCR, and transcript initiation was mapped for all three genes using the RNA ligase-mediated 5' rapid amplification of cDNA ends technique. PpDhn3 transcripts from bark collected in December or July, as well as transcripts from developing fruit, initiated at a single site. Although most of the PpDhn1 transcripts initiated at a similar position, those from young fruit initiated much further upstream of the consensus TATA box. Bark and fruit transcripts encoding PpDhn2 initiated ca. 30 bases downstream of a consensus TATA box; however, transcripts from ripe fruit initiated further upstream. Ripe fruit transcripts of PpDhn2 contain a 5' leader intron which is predicted to add some 34 amino acids to the N-terminal methionine of the cognate protein when properly processed. Secondary structure prediction of sequences surrounding the TATA box suggests that conformational transitions associated with decreasing temperature contribute to the regulation of expression of the cold-responsive dehydrin genes. Taken together these results reveal new, unexpected levels of gene regulation contributing to the overall expression pattern of peach dehydrins.

Characterization of an S-locus receptor protein kinase-like gene from peach.

A receptor-like protein kinase gene (Ppsrkl1) was isolated from a peach (Prunus persica (L.) Batsch.) bark cDNA library prepared with RNAs isolated from bark collected in December (cold acclimated). Sequence analysis indicated that this gene is related to the S-locus family of receptor protein kinases (SRKs) and that it shares greatest homology with ZMPK1 from maize and At4g32300 from Arabidopsis, both of which are intron-less genes. In bark tissues, Ppsrkl1 is induced by water deficit treatment, repressed by short-day photoperiods and showed no response to cold treatment. The Ppsrkl1 mRNA also increased in roots in response to water deficit. In fruit, Ppsrkl1 shows no response up to 6 h after wounding, but at 12 and 24 h after wounding, Ppsrkl1 mRNA shows an abrupt decline. This decline was prevented by the addition of salicylic acid to the wound site. The Ppsrkl1 mRNA rapidly decreased in fruit after 10-min exposure to UV-C radiation, followed by a return to normal levels within 1.5 h. Taken together, these experiments indicate that Ppsrkl1 is negatively regulated by light and positively influenced by salicylic acid treatment in fruit and water stress in bark and roots.