Marchetti Adrian, Moreno Carly M, Cohen Natalie R, Oleinikov Irina, deLong Kimberly, Twining Benjamin S, Armbrust E Virginia, Lampe Robert H
Department of Marine Sciences, University of North Carolina at Chapel Hill, CB 3300, Chapel Hill, North Carolina, 27599, USA.
Department of Biomedical Science, Florida Atlantic University, 777 Glades Road, BC-71, Boca Raton, Florida, 33431, USA.
J Phycol. 2017 Aug;53(4):820-832. doi: 10.1111/jpy.12539. Epub 2017 May 10.
Iron availability limits primary productivity in large areas of the world's oceans. Ascertaining the iron status of phytoplankton is essential for understanding the factors regulating their growth and ecology. We developed an incubation-independent, molecular-based approach to assess the iron nutritional status of specific members of the diatom community, initially focusing on the ecologically important pennate diatom Pseudo-nitzschia. Through a comparative transcriptomic approach, we identified two genes that track the iron status of Pseudo-nitzschia with high fidelity. The first gene, ferritin (FTN), encodes for the highly specialized iron storage protein induced under iron-replete conditions. The second gene, ISIP2a, encodes an iron-concentrating protein induced under iron-limiting conditions. In the oceanic diatom Pseudo-nitzschia granii (Hasle) Hasle, transcript abundance of these genes directly relates to changes in iron availability, with increased FTN transcript abundance under iron-replete conditions and increased ISIP2a transcript abundance under iron-limiting conditions. The resulting ISIP2a:FTN transcript ratio reflects the iron status of cells, where a high ratio indicates iron limitation. Field samples collected from iron grow-out microcosm experiments conducted in low iron waters of the Gulf of Alaska and variable iron waters in the California upwelling zone verify the validity of our proposed Pseudo-nitzschia Iron Limitation Index, which can be used to ascertain in situ iron status and further developed for other ecologically important diatoms.
铁的可利用性限制了世界上大片海洋区域的初级生产力。确定浮游植物的铁状态对于理解调节其生长和生态的因素至关重要。我们开发了一种不依赖培养的、基于分子的方法来评估硅藻群落特定成员的铁营养状况，最初聚焦于具有重要生态意义的羽纹硅藻假微型海链藻。通过比较转录组学方法，我们鉴定出两个能高度准确追踪假微型海链藻铁状态的基因。第一个基因，铁蛋白（FTN），编码在铁充足条件下诱导产生的高度特化的铁储存蛋白。第二个基因，ISIP2a，编码在铁限制条件下诱导产生的一种铁浓缩蛋白。在海洋硅藻格氏假微型海链藻（哈斯勒）哈斯勒中，这些基因的转录本丰度直接与铁可利用性的变化相关，在铁充足条件下FTN转录本丰度增加，在铁限制条件下ISIP2a转录本丰度增加。由此产生的ISIP2a:FTN转录本比率反映了细胞的铁状态，比率高表明铁限制。从在阿拉斯加湾低铁水域和加利福尼亚上升流区可变铁水域进行的铁培养扩大微宇宙实验中采集的现场样本，验证了我们提出的假微型海链藻铁限制指数的有效性，该指数可用于确定原位铁状态，并可进一步应用于其他具有重要生态意义的硅藻。
