Zarina Zainuddin

A review on non-syndromic tooth agenesis associated with PAX9 mutations

Summary Tooth agenesis in the reduction of tooth number which includes hypodontia, oligodontia and anodontia is caused by disturbances and gene mutations that occur during odontogenesis. To date, several genetic mutations that unlock the causes of non-syndromic tooth agenesis are being discovered; these have been associated with certain illnesses because tooth development involves the interaction of several genes for tooth epithelium and mesenchyme odontogenesis. Mutation of candidate genes PAX9 and MSX1 have been identified as the main causes of hypodontia and oligodontia; meanwhile, AXIN2 mutation is associated with anodontia. Previous study using animal models reported that PAX9-deficient knockout mice exhibit missing molars due to an arrest of tooth development at the bud stage. PAX9 frameshift, missense and nonsense mutations are reported to be responsible; however, the most severe condition showed by the phenotype is caused by haploinsufficiency. This suggests that PAX9 is dosage-sensitive. Understanding the mechanism of genetic mutations will benefit clinicians and human geneticists in future alternative treatment investigations.

Evaluation of genetic homogeneity of Jatropha curcas L. hybrid at an early stage of shoot bud formation from petioles using ISSR marker

ABSTRACT Genetic homogeneity is known to be the most important prerequisite in the micropropagation of Jatropha curcas L. to produce true-to-type plants. The detection of genetic homogeneity in clonal micropropagation for elite plants at an early stage is required, to avoid any increase in variation in the next stage of micropropagation. The genetic homogeneity was assessed during shoot bud formation from petiole explants of J.curcas (P1 × P3) hybrid with different concentrations of thidiazuron (TDZ) in a range of 0.5–4.0 mg/L using inter simple sequence repeat (ISSR) markers. Out of 23 ISSR primers, 16 primers produced clear, distinct and reproducible bands. A total of 96 bands, ranging in size from 100 to 1013 bp were generated. Based on the band data, a total of 94 bands were monomorphic (98%) and two bands were polymorphic (2%). All banding patterns from the shoot buds induced by 0.5, 1.0 and 2.0 mg/L TDZ were monomorphic, but 4.0 mg/L gave 2% polymorphism. These findings indicated that concentrations of 0.5, 1.0 and 2.0 mg/L TDZ did not trigger any somaclonal variation and could, therefore, be considered suitable for application in clonal micropropagation of J. curcas hybrid using petioles as explant material.

Selective isolation and antagonistic activity of actinomycetes from mangrove forest of Pahang, Malaysia

This study aimed to isolate and evaluate the antagonistic potential of actinomycetes from mangrove forest of Pahang, Malaysia. Sediment samples from seven different sites were pretreated using wet heat and dry heat methods followed by dilution plating on eight isolation media. In total, 4850 isolates were successfully recovered, with inorganic salt–starch agar displaying the highest percentage of recovery (31.7%), followed by actinomycete isolation agar (24.1%). The wet heat pretreatment was found to be more effective in the enumeration of actinomycetes, since 81.4% of total isolates were yielded using this technique, whereas dry heat treatment was better in the enumeration of spore-forming actinomycetes. After both pretreatments, Streptomyces-like and Micromonospora-like isolates were the most predominant. The antagonistic activities of the representative isolates were evaluated using the cross-streak method. In total, 78 isolates were active against at least one of the test organisms. Among them, 28.2% exhibited antibacterial activity, 23.1% exhibited antifungal activity and 48.7% displayed both. Nine isolates demonstrated broad antagonism by inhibiting the growth of all test organisms. The presence of a relatively large number of bioactive isolates suggests that Pahang mangrove forest is a potential source of actinomycetes with biosynthetic capabilities.