Finding signals for plant promoters

The strongest signal of plant promoter is searched with the model of single motif with two types. It turns out that the dominant type is the TATA-box. The other type may be called TATA-less signal, and may be used in gene finders for promoter recognition. While the TATA signals are very close for the monocot and the dicot, their TATA-less signals are significantly different. A general and flexible multi-motif model is also proposed for promoter analysis based on dynamic programming. By extending the Gibbs sampler to the dynamic programming and introducing temperature, an efficient algorithm is developed for searching signals in plant promoters.     

Mechanical signalling,calcium and plant form

Calcium is a dynamic signalling molecule which acts to transduce numerous signals in plant tissues. The basis of calcium signalling is outlined and the necessity for measuring and imaging of calcium indicated. Using plants genetically transformed with a cDNA for the calcium-sensitive luminescent protein, aequorin, we have shown touch and wind signals to immediately increase cytosol calcium. Touch and wind signal plant cells mechanically, through tension and compression of appropiate cells. Many plant tissues and cells are very sensitive to mechanical stimulation and the obvious examples of climbing plants, insectivorous species as well as other less well-known examples are described. Touch sensing in these plants may be a simple evolutionary modification of sensitive mechanosensing system present in every plant. The possibility that gravitropism may be a specific adaptation of touch sensing is discussed. There is a growing appreciation that plant form may have a mechanical basis. A simple mechanical mechanism specifying spherical, cylindrical and flat-bladed structures is suggested. The limited morphological variety of plant tissues may also reflect mechanical specification. The article concludes with a discussion of the mechanisms of mechanical sensing, identifying integrin-like molecules as one important component, and considers the specific role of calcium.     

Host plants impact courtship vibration transmission and mating success of a parasitoid wasp,Cotesia flavipes (Hymenoptera: Braconidae)

Host plants provide food, shelter, and mating habitats for herbivorous and parasitoid insects. Yet each plant species is a microhabitat with distinct chemical and physical attributes that may drive selection and diversification of insects. This study examines differences in courtship vibration signal transmission through leaves of three host plant species that vary in physical characteristics (leaf tissue density, leaf width and percent moisture) and how signal transmission relates to mating success for a parasitoid wasp. The vibration signals transmit with a longer duration and a higher relative amplitude in the host plant leaves of the species with the lowest leaf tissue density, which was also the plant type with the highest mating frequency. Host plants may be a selective force on courtship vibration signals and may contribute to the behavioral or genetic divergence of populations on different host plant species.     

The TATA-dependent and TATA-independent promoters of the Drosophila melanogaster actin 5C-encoding gene

The major cytoskeletal actin of Drosophila melanogaster, actin 5C, is encoded by a gene (act5C) that has two promoters which are differentially controlled and possess distinct sets of regulatory elements. The distal basal promoter has a TATA motif, but the proximal does not. The distal strong positive domain, centered at nucleotide -290, can be shifted and fused directly to the distal basal promoter without losing its activity. It can also activate heterologous basal promoters containing either TATAAAT or TATTTAA signal when directly fused to them, but cannot activate the basal proximal promoter, which is TATA-less. When the entire distal regulatory region, which includes a remote enhancer-like region, is fused to the proximal promoter, it does not increase the proximal promoter activity. Fusion of the distal strong negative domain to the proximal promoter does not inhibit activity. Thus, all the three major strong regulatory domains of the distal promoter are unable to act on the proximal promoter.