Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.
Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.
Harmful Algae. 2021 Mar;103:101995. doi: 10.1016/j.hal.2021.101995. Epub 2021 Feb 20.
The cosmopolitan, species-rich diatom genus Pseudo-nitzschia represents a good system for the study of speciation, evolution and diversity. Understanding elements linked to population dynamics and life cycle regulation for these species is of particular importance in view of their ability to produce the toxin domoic acid and cause harmful blooms. Pseudo-nitzschia multistriata, one of the toxic species that represents a model for the study of life cycle related questions, is the only diatom for which a sex determination mechanism has been described. Populations in the Gulf of Naples (Mediterranean Sea), can share four different allelic variants (A, M, B, N) of the mating type determination region, and one of them (A) is responsible for the determination of the mating type + (MT+), defined by the MT+ restricted expression of the gene MRP3. Here, we analysed the sex determination genomic region in three new strains isolated from the Gulf of Mexico and compared it to the alleles previously described in the Mediterranean strains. We first show that these geographically distant strains of P. multistriata belong to different populations but can interbreed. Next, we show that the two populations share an overall similar structure of the genomic locus although differences can be seen in the polymorphic regions upstream of MRP3. In strain P4-C1, we amplified and sequenced an allele (M) identical to one of those previously characterized in the Mediterranean strains. In the other two strains, P4-C2 and P4-C5, we identified three new alleles, which we named A2, B2 and N2. P4-C2 and P4-C5 are heterozygous and share the common allele A2 linked to the monoallelic expression of the MT+ specific sex determining gene MRP3. Our results expand information on the global distribution of P. multistriata and on the level of conservation of the sex determination region in different populations. The definition of the extent of intra- and inter-specific conservation of this region would be a relevant addition to our understanding of Pseudo-nitzschia diversity and evolution.
物种丰富的世界性硅藻属假菱形藻是研究物种形成、进化和多样性的良好系统。鉴于其产生毒素软骨藻酸并导致有害赤潮的能力，了解与这些物种的种群动态和生命周期调节相关的元素尤为重要。假菱形藻是研究与生命周期相关问题的模式生物之一，它是唯一一种描述了性别决定机制的硅藻。在那不勒斯湾（地中海）的种群可以共享交配型决定区域的四个不同等位基因变体（A、M、B、N），其中一个（A）负责决定交配型+（MT+），由 MRP3 基因的 MT+特异性表达来定义。在这里，我们分析了从墨西哥湾分离出的三个新菌株的性别决定基因组区域，并将其与以前在中菌株中描述的等位基因进行了比较。我们首先表明，这些地理位置遥远的假菱形藻菌株属于不同的种群，但可以杂交。接下来，我们表明，尽管在 MRP3 上游的多态区域可以看到差异，但两个种群的基因组位点具有总体相似的结构。在 P4-C1 菌株中，我们扩增并测序了一个与以前在中菌株中描述的等位基因（M）相同的等位基因。在另外两个菌株 P4-C2 和 P4-C5 中，我们鉴定了三个新的等位基因，我们将其命名为 A2、B2 和 N2。P4-C2 和 P4-C5 是杂合的，并共享与 MT+特异性性别决定基因 MRP3 的单等位基因表达相关的共同等位基因 A2。我们的结果扩展了假菱形藻在全球分布的信息，以及不同种群中性别决定区域的保守程度。该区域的种内和种间保守程度的定义将是我们对假菱形藻多样性和进化理解的一个重要补充。
