Vacuolar processing enzyme activates programmed cell death in the apical meristem inducing loss of apical dominance

The potato (Solanum tuberosum L.) tuber is a swollen underground stem that can sprout in an apical dominance (AD) pattern. Bromoethane (BE) induces loss of AD and the accumulation of vegetative vacuolar processing enzyme (S. tuberosum vacuolar processing enzyme [StVPE]) in the tuber apical meristem (TAM). Vacuolar processing enzyme activity, induced by BE, is followed by programmed cell death in the TAM. In this study, we found that the mature StVPE1 (mVPE) protein exhibits specific activity for caspase 1, but not caspase 3 substrates. Optimal activity of mVPE was achieved at acidic pH, consistent with localization of StVPE1 to the vacuole, at the edge of the TAM. Downregulation of StVPE1 by RNA interference resulted in reduced stem branching and retained AD in tubers treated with BE. Overexpression of StVPE1 fused to green fluorescent protein showed enhanced stem branching after BE treatment. Our data suggest that, following stress, induction of StVPE1 in the TAM induces AD loss and stem branching

High coverage metabolomics analysis reveals phage-specific alterations to Pseudomonas aeruginosa physiology during infection

&lt;p&gt;Phage-mediated metabolic changes in bacteria are hypothesized to markedly alter global nutrient and biogeochemical cycles. Despite their theoretic importance, experimental data on the net metabolic impact of phage infection on the bacterial metabolism remains scarce. In this study, we tracked the dynamics of intracellular metabolites using untargeted high coverage metabolomics in Pseudomonas aeruginosa cells infected with lytic bacteriophages from six distinct phage genera. Analysis of the metabolomics data indicates an active interference in the host metabolism. In general, phages elicit an increase in pyrimidine and nucleotide sugar metabolism. Furthermore, clear phage-specific and infection stage-specific responses are observed, ranging from extreme metabolite depletion (for example, phage YuA) to complete reorganization of the metabolism (for example, phage phiKZ). As expected, pathways targeted by the phage-encoded auxiliary metabolic genes (AMGs) were enriched among the metabolites changing during infection. The effect on pyrimidine metabolism of phages encoding AMGs capable of host genome degradation (for example, YuA and LUZ19) was distinct from those lacking nuclease-encoding genes (for example, phiKZ), which demonstrates the link between the encoded set of AMGs of a phage and its impact on host physiology. However, a large fraction of the profound effect on host metabolism could not be attributed to the phage-encoded AMGs. We suggest a potentially crucial role for small, &amp;#39;non-enzymatic&amp;#39; peptides in metabolism take-over and hypothesize on potential biotechnical applications for such peptides. The highly phage-specific nature of the metabolic impact emphasizes the potential importance of the &amp;#39;phage diversity&amp;#39; parameter when studying metabolic interactions in complex communities.&lt;/p&gt;</p