Polymorphism study of growth differentiation factor 9B (GDF9B) gene and its association with reproductive traits in sheep

GDF9B protein plays a critical role in growth and differentiation of early ovarian follicles. In Inverdale and Hanna sheep, mutations in exon-2 of GDF9B gene have been recorded to show increased ovulation rate in heterozygous condition whereas homozygotes are infertile. Present screen study was carried out to explore the presence of these reported mutations in Corriedale and Local Kashmir Valley sheep with high rate of twinning. Exon-2 of GDF9B gene was amplified and the polymorphism was explored by SSCP technique. In the process three different bandings were observed. Later on these patterns corresponded with three different allelic forms on nucleotide sequencing. Phylogenetic analysis revealed that the nucleotide sequences of alleles observed in the present study and that of a published sequence of sheep were having the same point of origin. The results were also compared with goats, large ruminants and humans. The allelic frequencies of allele A and B were 0.64 and 0.36, respectively in Corriedale sheep whereas the allelic frequencies of all the three alleles in Kashmir Valley sheep were 0.60, 0.34 and 0.06. SNP “C” of the designated genotype AC was observed to pronounce a significant effect on litter size with average litter size going up by 0.63 as compared with the nearest genotype AB wherein the litter size was 1.29 ± 0.05. The average litter size between AA and AB genotypes did not vary significantly.     

Apple has two orthologues of FLORICAULA/LEAFY involved in flowering

Two orthologues of FLORICAULA/LEAFY, AFL1 and AFL2 (apple FLO/LFY), were isolated from the floral buds of apple trees. Their expression was detected in various tissues and during differentiation of the floral buds. Furthermore, the flowering effectiveness of each gene was assessed with transgenic Arabidopsis. Both AFL1 and AFL2 showed high homology to each other (90%) and a high degree of similarity to PTLF and PEAFLO (70%), which are homologues of FLO/LFY from poplar and pea, respectively. RNA blot analysis showed that AFL1 was expressed only in the floral bud during the transition from vegetative to reproductive growth, whereas AFL2 was expressed in vegetative shoot apex, floral buds, floral organs and root. Genomic Southern analysis showed that apple had other homologues in addition to AFL1 and AFL2. The transgenic Arabidopsis with over-expressed AFL2 showed accelerated flowering and gave rise to several solitary flowers from rosette axils directly. AFL1 had similar effects, but the phenotypes of the transgenic Arabidopsis with AFL1 were weaker than those with AFL2. These results suggest that both genes are involved in flower differentiation in apple.     

Structure of the Alkalohyperthermophilic Archaeoglobus fulgidus Lipase Contains a Unique C-Terminal Domain Essential for Long-Chain Substrate Binding

Several crystal structures of AFL, a novel lipase from the archaeon Archaeoglobus fulgidus, complexed with various ligands, have been determined at about 1.8 Å resolution. This enzyme has optimal activity in the temperature range of 70-90 °C and pH 10-11. AFL consists of an N-terminal α/β-hydrolase fold domain, a small lid domain, and a C-terminal β-barrel domain. The N-terminal catalytic domain consists of a 6-stranded β-sheet flanked by seven α-helices, four on one side and three on the other side. The C-terminal lipid binding domain consists of a β-sheet of 14 strands and a substrate covering motif on top of the highly hydrophobic substrate binding site. The catalytic triad residues (Ser136, Asp163, and His210) and the residues forming the oxyanion hole (Leu31 and Met137) are in positions similar to those of other lipases. Long-chain lipid is located across the two domains in the AFL-substrate complex. Structural comparison of the catalytic domain of AFL with a homologous lipase from Bacillus subtilis reveals an opposite substrate binding orientation in the two enzymes. AFL has a higher preference toward long-chain substrates whose binding site is provided by a hydrophobic tunnel in the C-terminal domain. The unusually large interacting surface area between the two domains may contribute to thermostability of the enzyme. Two amino acids, Asp61 and Lys101, are identified as hinge residues regulating movement of the lid domain. The hydrogen-bonding pattern associated with these two residues is pH dependent, which may account for the optimal enzyme activity at high pH. Further engineering of this novel lipase with high temperature and alkaline stability will find its use in industrial applications.