Search

Genetic sub-populations (clades) of cosmopolitan marine diatom Pseudo-nitzschia pungens might have distinct habitats, and their hybrid zone is suspected in higher latitude area of the West Pacific area, however, it is still unrevealed because of technical difficulties and lack of evidences in natural environments. The aim of this study is to investigate the habitat characteristics of each clade of P. pungens on geographical distribution with the habitat temperature ranges of each clade and to reveal their hybrid zone in the West Pacific area. We employed the 137 number of nucleotide sequences of P. pungens and its sampling data (spatial and temporal scale) originated from the West Pacific area, and used field application of qPCR assay for intra-specific level of P. pungens . Only two genotypes, clade I and III, were identified in the West Pacific area. Clade I was distributed from 39 to 32.3°N, and clade III were from 1.4 to 34.4°N. The estimated habitat temperature for the clade I and clade III ranges were 8.1–26.9 °C and 24.2–31.2 °C, respectively. The latitudinal distributions and temperature ranges of each clade were significantly different. The qPCR assay employed, and results suggested that the hybrid zone for clade I and III has been observed in the southern Korean coasts, and clade III might be introduced from the Southern Pacific area. The cell abundances of clade III were strongly related with the higher seawater temperature and warm current force. This study has defined distinct habitat characteristics of genetically different sub-populations of P. pungens , and revealed its hybrid zone in natural environment for the first time. We also provided strong evidences about dispersion of the population of clade III to higher latitude in the West Pacific area. [ABSTRACT FROM AUTHOR]

Three genetic sub-populations (clade I, II and III) of Pseudo-nitzschia pungens , the potential toxic marine diatom, are known to have distinguishable growth characteristics under different culture conditions and distinct distributed patterns in the world. However, to date their exact eco-physiological traits are unrevealed in fields due to lack of the method to detect and/or measure abundances of each sub-populations, hence, the qPCR (quantitative real-time polymerase chain reaction) assay was developed to detect and quantify the P. pungens cells of each clade. Designed two specific primer sets, Pcla12F/R (for clade I and II) and Pcla3F/R (for clade III) only could amplify each target genomic DNA. The, significant linear relationships (R 2 > 0.998) was established between C t (threshold cycle) value and the log of cell abundance for each clade. Through the melting curve analysis, comparisons for gene copy numbers among the three clades and spike test for field study, our qPCR assay was reliable to quantify the cell numbers of each clade. There was strong linear correlation (R 2 > 0.990) between cell abundances as estimated by qPCR assay and direct counting via light microscope in spike test, and 0.24 (clade I), 0.25 (clade II) and 0.33 (clade III) P. pungens cells per mL were detected markedly upon the use of specific two-primer set. Finally, developed qPCR assay was applied on field samples successfully. Our study implicate that our qPCR assay is an accurate and sensitive technique to estimate the cell abundances of each clade of P. pungens in field works. [ABSTRACT FROM AUTHOR]