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Environmental signalling in a marine diatom

Marine diatoms are responsible for approximately a quarter of global photosynthetic carbon fixation. Despite this, our understanding of diatom physiology remains limited. Iron is a key limiting nutrient in the oceans and understanding the cellular mechanisms underlying the response of diatoms to iron-limitation will provide important information on the factors limiting global primary productivity. Analyses of the response of the marine diatom Phaeodactylum tricornutum to iron limitation indicate oxidative stress and Ca2+ signalling play important roles (1, 2). This project will explore the function of two putative annexins in the P. tricornutum genome which are strongly upregulated following iron limitation. Annexins are soluble, multifunctional proteins which have proposed roles in coordinating reactive oxygen species and Ca2+ signalling networks (3). Annexins are capable of calcium-dependent membrane attachment or insertion and can form calcium-permeable channels in plants and animals (3). Advanced molecular genetic techniques available in P. tricornutum will enable localisation of annexins through fusion to green fluorescent protein (GFP) and targeted knockdown of annexin expression through RNA interference. Annexin protein sequences will be analysed for conserved sequences, particularly metal binding sites. Heterologously expressed annexins will be tested for peroxidase and calcium channel activity to ascertain whether they could participate in oxidative stress protection (3) and calcium signalling (2). The project is jointly supervised by Dr. Glen Wheeler, Plymouth Marine Laboratory.

  1. PNAS USA 105 10438
  2. Science 288 2363
  3. New Phytologist 189 40