Twenty-four accessions of genus Amaranthus belong to ten different species distributed worldwide were analysed using variation of isozymes and allozymes patterns to obtain better insight into genetic diversity and evolutionary relationships within and between these taxonomic entities. Enzyme electrophoresis resulted in clear staining for five enzyme systems including acid phosphatase, alkaline phosphatase, α-esterase, β-esterase and peroxidase. Eighteen putative isozyme loci were scored. Only one locus (Alp2) was found to be monomorphic for all accessions, whereas all other loci were polymorphic. A total of 40 alleles were recognised across all loci. Frequencies of 14 loci were found to discriminate significantly among the 24 studied accessions (p < 0.05). The mean number of polymorphic alleles per locus A = 1.47 and percentage of polymorphic loci P = 38.195% were found to be lower than that reported ones for herbaceous forage plants (A = 1.93 and P = 53.3%). This reduction could be due to geographical isolation, which terminates the gene flow among the studied accessions. The estimates of accessions genetic structure using Nei genetic diversity statistics were calculated. The averages of total heterozygosity (HT) and intra-accessional genetic diversity (HS) were 0.44 and 0.14, respectively. Moreover, the inter-accessional genetic diversity DST has an average of 0.301. These results indicated that inter-accession genetic diversity is higher than intra-accession one. The high levels of genetic differentiation among accessions GST = 0.692, x2 = 48.318, p > 0.05; and the inter-accessional genetic diversity (DST) = 0.301 were probably indicative of low gene flow. This result was confirmed by the gene flow estimates NmW = 0.1164 and indicated the presence of a high percentage of self-pollination in the plant.
Caveolin-3 (cav-3) mutations are linked to the long-QT syndrome (LQTS) causing distinct clinical symptoms. Hyperpolarization-activated cyclic nucleotide channel 4 (HCN4) underlies the pacemaker current If. It associates with cav-3 and both form a macromolecular complex.
To examine the effects of human LQTS-associated cav-3 mutations on HCN4-channel function, HEK293-cells were cotransfected with HCN4 and wild-type (WT) cav-3 or a LQTS-associated cav-3 mutant (T78M, A85T, S141R, or F97C). HCN4 currents were recorded using the whole-cell patch-clamp technique.
WT cav-3 significantly decreased HCN4 current density and shifted midpoint of activation into negative direction. HCN4 current properties were differentially modulated by LQTS-associated cav-3 mutations. When compared with WT cav-3, A85T, F97C, and T78M did not alter the specific effect of cav-3, but S141R significantly increased HCN4 current density. Compared with WT cav-3, no significant modifications of voltage dependence of steady-state activation curves were observed. However, while WT cav-3 alone had no significant effect on HCN4 current activation, all LQTS-associated cav-3 mutations significantly accelerated HCN4 activation kinetics.
Our results indicate that HCN4 channel function is modulated by cav-3. LQTS-associated mutations of cav-3 differentially influence pacemaker current properties indicating a pathophysiological role in clinical manifestations.