ABC Transporters in Prorocentrum lima and Their Expression Under Different Environmental Conditions Including Okadaic Acid Production

Abstract

Prorocentrum lima is a typical benthic toxic dinoflagellate, which can produce phycotoxins such as okadaic acid (OA). In this study, we identified three ABC transporter genes (ABCB1, ABCC1 and ABCG2) and characterized their expression patterns, as well as OA production under different environmental conditions in P. lima. We found that the three ABC transporters all showed high identity with related ABC proteins from other species, and contained classical features of ABC transport proteins. Among them, ABCG2 was a half size transporter. The three ABC transporter genes displayed various expression profiles under different conditions. The high concentration of Cu2+ could up-regulate ABCB1, ABCC1 and ABCG2 transcripts in P. lima, suggesting the potential defensive role of ABC transporters against metal ions in surrounding waters. Cu2+, in some concentration, could induce OA production; meanwhile, tributyltin inhibited OA accumulation. The grazer Artemia salina could induce OA production, and P. lima displayed some toxicity to the grazer, indicating the possibility of OA as an anti-grazing chemical. Collectively, our results revealed intriguing data about OA production and the expression patterns of three ABC transporter genes. However, we could not find any significant correlation between OA production and expression pattern of the three ABC transporters in P. lima. Our results might provide new molecular insights on the defensive responses of P. lima to the surrounding environment.

High Value Phycotoxins From the Dinoflagellate Prorocentrum

“…(Fernández et al, 2003;Hoppenrath et al, 2013;Luo et al, 2017;Pan et al, 2017;Nishimura et al, 2020). For example, all reported Prorocentrum lima strains produce OA and some strains also produce DTX1 as a minor toxin (Jackson et al, 1993;McLachlan et al, 1994;Vanucci et al, 2010;Varkitzi et al, 2010;Hoppenrath et al, 2013;Wang et al, 2015;Hou et al, 2016;Lee et al, 2016;Hoppenrath, 2017;Pan et al, 2017;Aquino-Cruz et al, 2018;Gu et al, 2019). Prorocentrum belizeanum, caipirignum, concavum, maculosum and hoffmannianum are also known producers of DSP toxins (Morton et al, 1994;Zhou and Fritz, 1994;Hoppenrath et al, 2013;López-Rosales et al, 2014;Luo et al, 2017;Accoroni et al, 2018;Rodríguez et al, 2018;Lim et al, 2019;Lee et al, 2020).…”

“…It has been speculated that the low chlorophyll a to carbon ratio is responsible for the slow growth of dinoflagellates (Tang, 1996) but the chlorophyll a content per unit mass of dinoflagellates is similar to diatoms (Gallardo- Rodríguez et al, 2012). Several studies have focused on small-scale cultures of benthic dinoflagellates to optimize growth rates and toxic production (Jackson et al, 1993;McLachlan et al, 1994;Morton et al, 1994;Yang et al, 2008;Zhong et al, 2008;Li et al, 2009;Vanucci et al, 2010;Varkitzi et al, 2010;López-Rosales et al, 2014;Wang et al, 2015;Hou et al, 2016;Accoroni et al, 2018;Aquino-Cruz et al, 2018;Gu et al, 2019;Lee et al, 2020). In a typical photosynthetic culture the maximum biomass concentration reached was well below 1 g/L and regarding phycotoxin production it is of the order of picograms (Gallardo- Rodríguez et al, 2012).…”

“…The effects of key environmental factors (e.g., nutrients, temperature, salinity, and light availability) on the phycotoxin production are species dependent (Vanucci et al, 2010;Varkitzi et al, 2010;Wang et al, 2015;Aquino-Cruz et al, 2018;Gu et al, 2019;Lee et al, 2020). Nutrient limitation is the most common strategy used to boost phycotoxin production, however as a result of nutrient limitation cell growth usually declines.…”

“…Benthic Prorocentrum spp. has been cultured using nitrate, ammonium and urea (Table 2) (McLachlan et al, 1994;Pan et al, 1999;Zhong et al, 2008;Li et al, 2009;Varkitzi et al, 2010;Hou et al, 2016;Accoroni et al, 2018;Gu et al, 2019;Lee et al, 2020). Whereas some studies suggest that nitrogen concentration is directly proportional to the maximum cell density but not growth rate (Zhong et al, 2008;Vanucci et al, 2010;Hou et al, 2016), others found that it is directly proportional to both (McLachlan et al, 1994;Li et al, 2009).…”

Chemical Defense in Marine Organisms

“…Prorocentrum lima is another toxic dinoflagellate, which can produce phycotoxins such as okadaic acid (OA). Gu and co-workers [ 45 ] here identify three ABC transporter genes (ABCB1, ABCC1 and ABCG2) and characterize their expression patterns as well as OA production under different environmental conditions in P. lima . For example, they observed that Cu 2+ exposure could up-regulate ABCB1, ABCC1 and ABCG2 transcripts, suggesting a defensive role of ABC transporters against metal ions in surrounding waters.…”