A mechanism for bacteria to monitor the status of their vital cell wall peptidoglycan is suggested by the convergence of two phenomena: peptidoglycan recycling and beta‐lactamase induction. ampG and ampD, genes essential for beta‐lactamase regulation, are here shown to be required for recycling as well. Cells lacking either AmpG or AmpD lose up to 40% of their peptidoglycan per generation, whereas Escherichia coli normally suffers minimal losses and instead recycles 40 or 50% of the tripeptide, L‐alanyl‐D‐glutamyl‐meso‐diaminopimelic acid, from its peptidoglycan each generation. The ampG mutant releases peptidoglycan‐derived material into the medium. In contrast, the ampD mutant accumulates a novel cell wall muropeptide, 1,6‐anhydro N‐acetylmuramyl‐L‐alanyl‐D‐glutamyl‐meso‐diaminopimelic acid (anhMurNAc‐tripeptide), in its cytoplasm. This work suggests that AmpG is the permease for a large muropeptide and AmpD is a novel cytosolic N‐acetylmuramyl‐L‐alanine amidase that cleaves anhMurNAc‐tripeptide to release tripeptide, which is then recycled. These results also suggest that the phenomenon of beta‐lactamase induction is regulated by the level of muropeptide(s) in the cytoplasm, since an ampD mutation that results in beta‐lactamase expression even in the absence of a beta‐lactamase inducer coincides with accumulation of anhMurNAc‐tripeptide. The transcriptional regulator AmpR is presumably converted into an activator for beta‐lactamase production by sensing the higher level of muropeptide(s). This may be an example of a general mechanism for signaling the progress of external events such as cell wall maturation, cell division or cell wall damage.

During their lifetime, plants encounter numerous biotic and abiotic stresses with diverse modes of attack. Phytohormones, including salicylic acid (SA), ethylene (ET), jasmonate (JA), abscisic acid (ABA), auxin (AUX), brassinosteroid (BR), gibberellic acid (GA), cytokinin (CK) and the recently identified strigolactones (SLs), orchestrate effective defense responses by activating defense gene expression. Genetic analysis of the model plant Arabidopsis thaliana has advanced our understanding of the function of these hormones. The SA- and ET/JA-mediated signaling pathways were thought to be the backbone of plant immune responses against biotic invaders, whereas ABA, auxin, BR, GA, CK and SL were considered to be involved in the plant immune response through modulating the SA-ET/JA signaling pathways. In general, the SA-mediated defense response plays a central role in local and systemic-acquired resistance (SAR) against biotrophic pathogens, such as Pseudomonas syringae, which colonize between the host cells by producing nutrient-absorbing structures while keeping the host alive. The ET/JA-mediated response contributes to the defense against necrotrophic pathogens, such as Botrytis cinerea, which invade and kill hosts to extract their nutrients. Increasing evidence indicates that the SA- and ET/JA-mediated defense response pathways are mutually antagonistic.

Straight to the point! Preactivation of a p‐tolyl thioglycoside donor, followed by sequential addition of p‐tolyl thioglycosyl acceptors in one reaction flask allowed rapid syntheses of oligosaccharides independent of anomeric reactivities of donors and acceptors (see scheme). This strategy greatly streamlines the assembly of oligosaccharides.

Agriculture is largely dependent on climate and is highly vulnerable to climate change. The global mean surface temperatures are increasing due to global climate change. Temperature beyond the physiological optimum for growth induces heat stress in plants causing detrimental and irreversible damage to plant development, growth, as well as productivity. Plants have evolved adaptive mechanisms in response to heat stress. The classical plant hormones, such as auxin, abscisic acid (ABA), brassinosteroids (BRs), cytokinin (CK), salicylic acid (SA), jasmonate (JA), and ethylene (ET), integrate environmental stimuli and endogenous signals to regulate plant defensive response to various abiotic stresses, including heat. Exogenous applications of those hormones prior or parallel to heat stress render plants more thermotolerant. In this review, we summarized the recent progress and current understanding of the roles of those phytohormones in defending plants against heat stress and the underlying signal transduction pathways. We also discussed the implication of the basic knowledge of hormone-regulated plant heat responsive mechanism to develop heat-resilient plants as an effective and efficient way to cope with global warming.

Highly efficient syntheses of hyaluronic acid oligosaccharides have been accomplished through the pre-activation based iterative one-pot strategy. A series of oligosaccharides ranging from di-to hexasaccharides were rapidly assembled using only near stoichiometric amounts of the building blocks without aglycon adjustment or purifications of intermediate oligosaccharides. Deprotection and oxidation protocols were developed for protective group removal and oxidation-state adjustment. The availability of such structurally well defined synthetic hyaluronic acid oligosaccharides will greatly facilitate the establishment of detailed structure-function relationships.