The novel gene<Emphasis Type="Italic"> CpEdi-9</Emphasis> from the resurrection plant<Emphasis Type="Italic"> C. plantagineum</Emphasis> encodes a hydrophilic protein and is expressed in mature seeds as well as in response to dehydration in leaf phloem tissues

The resurrection plant Craterostigma plantagineum Hochst. is used as an experimental system to investigate desiccation tolerance in higher plants. A search for genes activated during early stages of dehydration identified the gene CpEdi-9, which is expressed in mature seeds and in response to dehydration in the phloem cells of vascular tissues of leaves. Elements for the tissue-specific expression pattern reside in the isolated promoter of the CpEdi-9 gene, as shown through the analysis of transgenic plants. The CpEdi-9 promoter could be a suitable tool for expressing genes in the vascular system of dehydrated plants. CpEdi-9 encodes a small (10 kDa) hydrophilic protein, which does not have significant sequence homologies to known genes. The predicted protein CpEDI-9 shares some physicochemical features with LEA proteins from plants and a nematode. Based on the unique expression pattern and on the nucleotide sequence we propose that CpEdi-9 defines a new class of hydrophilic proteins that are supposed to contribute to cellular protection during dehydration. This group of proteins may have evolved because desiccation tolerance requires the abundant expression of protective proteins during early stages of dehydration in all tissues.Abbreviations ABA Abscisic acid - ABRE ABA-responsive element - Edi Early dehydration induced - GUS Glucuronidase - LEA Late embryogenesis abundant - MU Methylumbelliferone This article is dedicated to Prof. Dr. Francesco Salamini on the occasion of his 65th birthday and his departure from the Max Planck Institute in Köln     

Regulation of expression of two aquaporin homologs in the intestine of the European eel: effects of seawater acclimation and cortisol treatment

Complementary DNAs encoding homologs of the mammalian aquaglyceroporins (termed AQPe) and aquaporin-1 isoforms (termed AQP1) were isolated from the European eel. The AQP amino acid sequences share 35-54% identity with other known human AQPs. Although AQPe mRNA expression was approximately equivalent along the entire length of the gut, AQP1 expression was the highest in the posterior/rectal segment. Seawater (SW) acclimation increased AQP1 mRNA abundance by 5- and 17-fold in the anterior, 14- and 23-fold in the mid-, and 9- and 7-fold in the posterior/rectal gut regions of yellow and silver eels, respectively. SW acclimation had an effect on AQPe mRNA expression only in the midintestine of silver eels, where a small but significant 1.7-fold increase in abundance was measured. Western blots using an eel AQP1-specific antibody identified the presence of a major immunoreactive 28-kDa protein, primarily within the posterior/rectal segment. A 3-wk SW transfer induced an increase in AQP1 protein abundance in all intestinal segments, with the posterior/rectal region still expressing protein levels approximately 40- and 8-fold higher than the anterior and midsegments, respectively. Strong AQP1 immunofluorescence was detected within the vascular endothelium in both freshwater (FW)- and SW-acclimated eels and in the epithelial apical brush border in the posterior/rectal gut regions of SW-acclimated eels. Cortisol infusion into FW eels had no effect on intestinal AQPe mRNA expression but induced increases in AQP1 mRNA and protein levels. These results provide evidence for the presence of a SW-induced and steroid-regulated AQP water channel pathway within the intestine of the European eel.     

The dog and rat olfactory receptor repertoires

Background

Dogs and rats have a highly developed capability to detect and identify odorant molecules, even at minute concentrations. Previous analyses have shown that the olfactory receptors (ORs) that specifically bind odorant molecules are encoded by the largest gene family sequenced in mammals so far.

Results

We identified five amino acid patterns characteristic of ORs in the recently sequenced boxer dog and brown Norway rat genomes. Using these patterns, we retrieved 1,094 dog genes and 1,493 rat genes from these shotgun sequences. The retrieved sequences constitute the olfactory receptor repertoires of these two animals. Subsets of 20.3% (for the dog) and 19.5% (for the rat) of these genes were annotated as pseudogenes as they had one or several mutations interrupting their open reading frames. We performed phylogenetic studies and organized these two repertoires into classes, families and subfamilies.

Conclusion

We have established a complete or almost complete list of OR genes in the dog and the rat and have compared the sequences of these genes within and between the two species. Our results provide insight into the evolutionary development of these genes and the local amplifications that have led to the specific amplification of many subfamilies. We have also compared the human and rat ORs with the human and mouse OR repertoires.     

Effects of stimuli shape and polarization in evoking deimatic patterns in the European cuttlefish, Sepia officinalis, under varying turbidity conditions

Cuttlefish possess the complex ability to identify approaching threats and then to selectively express the appropriate defense. We examined the visual cues used by Sepia officinalis cuttlefish during predator detection and the responses they selected. Using computer-generated stimuli, we set out to quantitate the deimatic responses to artificial looming stimuli of different shapes and contrasts. Defensive behavior gradually intensified as geometrical shapes resembled an image of a fish. Therefore, in addition to an object’s size or its sudden increase in size, cuttlefish use form recognition to identify a threat. Cuttlefish demonstrated equal performance in predator detection trough clear water when presented with intensity versus polarization contrasts. However, when the water turbidity increased, the cuttlefish still detected looming fish shapes based on polarization contrast even when intensity information alone did not suffice. These results demonstrate the interplay between intensity and polarization information transmission and processing in the spatial domain. As nectobenthic organisms, cuttlefish probably experience low visibility conditions on a regular basis. The ability to see further into turbid water and to better detect an approaching object would be beneficial for their survival.     

Convergent Evolution of Polysaccharide Debranching Defines a Common Mechanism for Starch Accumulation in Cyanobacteria and Plants

Starch, unlike hydrosoluble glycogen particles, aggregates into insoluble, semicrystalline granules. In photosynthetic eukaryotes, the transition to starch accumulation occurred after plastid endosymbiosis from a preexisting cytosolic host glycogen metabolism network. This involved the recruitment of a debranching enzyme of chlamydial pathogen origin. The latter is thought to be responsible for removing misplaced branches that would otherwise yield a water-soluble polysaccharide. We now report the implication of starch debranching enzyme in the aggregation of semicrystalline granules of single-cell cyanobacteria that accumulate both glycogen and starch-like polymers. We show that an enzyme of analogous nature to the plant debranching enzyme but of a different bacterial origin was recruited for the same purpose in these organisms. Remarkably, both the plant and cyanobacterial enzymes have evolved through convergent evolution, showing novel yet identical substrate specificities from a preexisting enzyme that originally displayed the much narrower substrate preferences required for glycogen catabolism.