Leaf surface structures enable the endemic Namib desert grass Stipagrostis sabulicola to irrigate itself with fog water.

The Namib grass Stipagrostis sabulicola relies, to a large degree, upon fog for its water supply and is able to guide collected water towards the plant base. This directed irrigation of the plant base allows an efficient and rapid uptake of the fog water by the shallow roots. In this contribution, the mechanisms for this directed water flow are analysed. Stipagrostis sabulicola has a highly irregular surface. Advancing contact angle is 98° ± 5° and the receding angle is 56° ± 9°, with a mean of both values of approximately 77°. The surface is thus not hydrophobic, shows a substantial contact angle hysteresis and therefore, allows the development of pinned drops of a substantial size. The key factor for the water conduction is the presence of grooves within the leaf surface that run parallel to the long axis of the plant. These grooves provide a guided downslide of drops that have exceeded the maximum size for attachment. It also leads to a minimum of inefficient drop scattering around the plant. The combination of these surface traits together with the tall and upright stature of S. sabulicola contributes to a highly efficient natural fog-collecting system that enables this species to thrive in a hyperarid environment.

Structure of the Haemophilus influenzae uvr-1+ gene: homology with other uvrC-like genes and characterization of the Haemophilus influenzae uvr-1 and uvr-2 mutations.

A 3.9 kb Haemophilus influenzae genomic DNA fragment was cloned in plasmid pUC9 that partially complemented the ultraviolet light sensitivity (UVs) of Escherichia coli uvrC mutant hosts. This fragment also complemented the UVs of H. influenzae uvr-1 (DB112) and uvr-2 (DB116) mutants. It genetically transformed the latter mutants to wild type UV resistance. The nucleotide (nt) sequence of this fragment revealed 3 open reading frames (ORFs). ORF2, now designated uvr-1+ (1746 nt), shows significant similarity in both the nt and amino acid (aa) composition to 7 complete proven or putative uvrC gene sequences. Computer analysis of the DNA sequence revealed several possible regulatory motifs 5' to uvr-1+, including a putative LexA-binding site as an inverted SOS box, located within the 3' region of ORF1, (extensive homology to the E. coli CMP-KDO synthetase gene), upstream of uvr-1+. Further computer analysis has also predicted that the four putative active site amino acids, located in the C-terminal half of each protein, are each situated in an area of secondary structure that are highly conserved.

Latent a1 VH germline genes in an a2a2 rabbit. Evidence for gene conversion at both the germline and somatic levels.

We have previously reported the sequences of putative latent a1 cDNA derived from an alpha 2 alpha 2 rabbit. Significant similarity to nominal a1 cDNA sequences was noted, but none of the latent sequences were completely a1-like. We have now probed a genomic library, produced from the same alpha 2 alpha 2 rabbit, for evidence of germline latent a1 VH genes. Four hundred ninety-four VH+ clones were screened with oligonucleotides specific for a1 diagnostic regions of framework region 1 (FR1) and FR3. Twenty-two percent of the VH+ clones hybridized with an a1FR3 oligonucleotide probe. Two a1 FR1 probes yielded weak signals with 6% to 13% of the VH+ clones. Twenty VH genes from clones positive for one or more of the a1-specific oligonucleotide probes were sequenced, revealing 14 unique germline VH genes. All but one of these genes were 85% to 92% identical to the VH1-a1 nominal gene prototype, with sequence identity extending into the leader intron. Most genes displayed extended regions of similarity to a1 in FR1, FR3, or both and expressed 13 to 17 of the 21 allotype-associated residues, consistent with the nominal a1 sequence. The a1-like sequences were variously interspersed with short non-a1 segments, suggestive of germline gene conversion. Although none of the germline a1-like VH genes we have isolated from the alpha 2 alpha 2 rabbits are identical to the known a1 genes or protein sequences from alpha 1 alpha 1 rabbits and 8 of 14 are pseudogenes, most could make significant contributions to the synthesis of a complete nominal a1 sequence by serving as a pool of sequence donors during somatic gene conversion.