Program
 
General Session 3: Biological oceanography & global change
 

 
 
1115
Influences of inorganic nitrogen and phosphorous on the transcriptional levels of nutrient transporters and genes in a tropical Pacific strain of Alexandrium minutum (Dinophyceae)
Monday 9th @ 1115-1135
Multi-function Hall
Hii Kieng Soon* , Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Lim Po Teen, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Leaw Chui Pin, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Presenter Email: chrleshii7007@yahoo.com
A marine dinoflagellate, Alexandrium minutum, is known to cause paralytic shellfish poisoning (PSP) incidences worldwide through the contamination of shellfish mollusks. Physiology and saxitoxin (STX) production of this species has been clarified after decades of studies. However, molecular basis of nutrient uptakes in relation to toxin production is limited. Therefore, ammonium transporter (AmAmt1), nitrate transporter (AmNrt2) and glutamine synthetase gene (AmGSIII) in a tropical Pacific strain of A. minutum were identified, and expression levels of these genes were studied under two nitrogen (N) sources, nitrate and ammonium. The physiology of N-uptakes by the cells showed that nitrate is preferable than ammonium. The cellular toxin quota (Qt) was higher at excess ammonium P-limited condition. The transcriptional response revealed that AmAmt1 was induced in nitrate condition, but suppressed at ammonium ambient. Conversely, AmNrt2 and AmGSIII were highly expressed in excess ammonium ambient. However, expressions of AmAmt1, AmNrt2 and AmGSIII were higher in low-P condition for both N sources. The results of this study revealed that uptakes of nitrate is more favorable than ammonium in A. minutum, and the transcription responses of those genes demonstrated a unique eco-physiological adaption for A. minutum to survive under unfavorable environmental condition, thus leading to successful bloom formation. It is hypothesized that STX is a byproduct of the cells to detoxify high NH4+ and release the environment stress.