Bacillus subtilis is the best-characterized member of the Gram-positive bacteria. Its genome of 4,214,810 base pairs comprises 4,100 protein-coding genes. Of these protein-coding genes, 53% are represented once, while a quarter of the genome corresponds to several gene families that have been greatly expanded by gene duplication, the largest family containing 77 putative ATP-binding transport proteins. In addition, a large proportion of the genetic capacity is devoted to the utilization of a variety of carbon sources, including many plant-derived molecules. The identification of five signal peptidase genes, as well as several genes for components of the secretion apparatus, is important given the capacity of Bacillus strains to secrete large amounts of industrially important enzymes. Many of the genes are involved in the synthesis of secondary metabolites, including antibiotics, that are more typically associated with Streptomyces species. The genome contains at least ten prophages or remnants of prophages, indicating that bacteriophage infection has played an important evolutionary role in horizontal gene transfer, in particular in the propagation of bacterial pathogenesis.

The continuing rise in atmospheric [CO2] is predicted to have diverse and dramatic effects on the productivity of agriculture, plant ecosystems and gas exchange. Stomatal pores in the epidermis provide gates for the exchange of CO2 and water between plants and the atmosphere, processes vital to plant life. Increased [CO2] has been shown to enhance anion channel activity proposed to mediate efflux of osmoregulatory anions (Cl- and malate(2-)) from guard cells during stomatal closure. However, the genes encoding anion efflux channels in plant plasma membranes remain unknown. Here we report the isolation of an Arabidopsis gene, SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1, At1g12480), which mediates CO2 sensitivity in regulation of plant gas exchange. The SLAC1 protein is a distant homologue of bacterial and fungal C4-dicarboxylate transporters, and is localized specifically to the plasma membrane of guard cells. It belongs to a protein family that in Arabidopsis consists of four structurally related members that are common in their plasma membrane localization, but show distinct tissue-specific expression patterns. The loss-of-function mutation in SLAC1 was accompanied by an over-accumulation of the osmoregulatory anions in guard cell protoplasts. Guard-cell-specific expression of SLAC1 or its family members resulted in restoration of the wild-type stomatal responses, including CO2 sensitivity, and also in the dissipation of the over-accumulated anions. These results suggest that SLAC1-family proteins have an evolutionarily conserved function that is required for the maintenance of organic/inorganic anion homeostasis on the cellular level.

With global warming, plant high temperature injury is becoming an increasingly serious problem. In wheat, barley, and various other commercially important crops, the early phase of anther development is especially susceptible to high temperatures. Activation of auxin biosynthesis with increased temperatures has been reported in certain plant tissues. In contrast, we here found that under high temperature conditions, endogenous auxin levels specifically decreased in the developing anthers of barley and Arabidopsis . In addition, expression of the YUCCA auxin biosynthesis genes was repressed by increasing temperatures. Application of auxin completely reversed male sterility in both plant species. These findings suggest that tissue-specific auxin reduction is the primary cause of high temperature injury, which leads to the abortion of pollen development. Thus, the application of auxin may help sustain steady yields of crops despite future climate change.

2Plants can acclimate by using tropisms to link the direction of growth to 41 environmental conditions. Hydrotropism allows roots to forage for water, a process 42 known to depend on abscisic acid (ABA) but whose molecular and cellular basis 43 remains unclear. Here, we show that hydrotropism still occurs in roots after laser 44 ablation removed the meristem and root cap. Additionally, targeted expression 45 studies reveal that hydrotropism depends on the ABA signalling kinase, SnRK2.2, and 46 the hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical 47 cells. Conversely, hydrotropism, but not gravitropism, is inhibited by preventing 48 differential cell-length increases in the cortex, but not in other cell types. We conclude 49 that root tropic responses to gravity and water are driven by distinct tissue-based 50 mechanisms. In addition, unlike its role in root gravitropism, the elongation zone 51 performs a dual function during a hydrotropic response, both sensing a water 52 potential gradient and subsequently undergoing differential growth. 53 3 Tropic responses are differential growth mechanisms that roots use to explore the 54 surrounding soil efficiently. In general, a tropic response can be divided into several steps, 55 comprising perception, signal transduction, and differential growth. All of these steps have 56 been well characterized for gravitropism, where gravity sensing cells in the columella of the 57 root cap generate a lateral auxin gradient, whilst adjacent lateral root cap cells transport 58 auxin to epidermal cells in the elongation zone, thereby triggering the differential growth that 59 drives bending [1][2][3][4] . In gravi-stimulated roots, the lateral auxin gradient is transported 60 principally by AUX1 and PIN carriers [3][4][5] . 61Compared with gravitropism, the tropic response to asymmetric water availability, i.e., 62 hydrotropism, has been far less studied. Previously, it was reported that surgical removal or 63 ablation of the root cap reduces hydrotropic bending in pea [6][7][8] and Arabidopsis thaliana 9 , 64suggesting that the machinery for sensing moisture gradients resides in the root cap. It has 65 also been reported that hydrotropic bending occurs due to differential growth in the 66 elongation zone 7,10 . However unlike gravitropism, hydrotropism in A. thaliana is independent 67 of AUX1 and PIN-mediated auxin transport 11,12 . Indeed, roots bend hydrotropically in the 68 absence of any redistribution of auxin detectable by auxin-responsive reporters 13,14 . 18,19 . 83However it is unclear whether this broad expression pattern is necessary for MIZ1's function 84 in hydrotropism or whether ABA signal transduction components in general have to be 85 expressed in specific root tip tissues for a hydrotropic response. The present study describes 86 a series of experiments in A. thaliana designed to identify the root tissues essential for a 87 hydrotropic response. We report that MIZ1 and a key ABA signal-transduction component 88SnRK2....

The main mechanism causing catabolite repression in Escherichia coli is the dephosphorylation of enzyme IIAGlc, one of the enzymes of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). The PTS is involved in the uptake of a large number of carbohydrates that are phosphorylated during transport, phosphoenolpyruvate (PEP) being the phosphoryl donor. Dephosphorylation of enzyme IIAGlc causes inhibition of uptake of a number of non-PTS carbon sources, a process called inducer exclusion. In this paper, we show that dephosphorylation of enzyme IIAGlc is not only caused by the transport of PTS carbohydrates, as has always been thought, and that an additional mechanism causing dephosphorylation exists. Direct monitoring of the phosphorylation state of enzyme IIAGlc also showed that many carbohydrates that are not transported by the PTS caused dephosphorylation during growth. In the case of glucose 6-phosphate, it was shown that transport and the first metabolic step are not involved in the dephosphorylation of enzyme IIAGlc, but that later steps in the glycolysis are essential. Evidence is provided that the [PEP]-[pyruvate] ratio, the driving force for the phosphorylation of the PTS proteins, determines the phosphorylation state of enzyme IIAGlc. The implications of these new findings for our view on catabolite repression and inducer exclusion are discussed.