Dasman Center for Research and Treatment of Diabetes, P.O Box 1180, Dasman, Kuwait.
Plant Sci. 2010 Nov;179(5):437-49. doi: 10.1016/j.plantsci.2010.07.001. Epub 2010 Jul 14.
The unicellular, halotolerant, green alga, Dunaliella salina (Chlorophyceae) has the unique ability to adapt and grow in a wide range of salt conditions from about 0.05 to 5.5M. To better understand the molecular basis of its salinity tolerance, a complementary DNA (cDNA) library was constructed from D. salina cells adapted to 2.5M NaCl, salt-shocked at 3.4M NaCl for 5h, and used to generate an expressed sequence tag (EST) database. ESTs were obtained for 2831 clones representing 1401 unique transcripts. Putative functions were assigned to 1901 (67.2%) ESTs after comparison with protein databases. An additional 154 (5.4%) ESTs had significant similarity to known sequences whose functions are unclear and 776 (27.4%) had no similarity to known sequences. For those D. salina ESTs for which functional assignments could be made, the largest functional categories included protein synthesis (35.7%), energy (photosynthesis) (21.4%), primary metabolism (13.8%) and protein fate (6.8%). Within the protein synthesis category, the vast majority of ESTs (80.3%) encoded ribosomal proteins representing about 95% of the approximately 82 subunits of the cytosolic ribosome indicating that D. salina invests substantial resources in the production and maintenance of protein synthesis. The increased mRNA expression upon salinity shock was verified for a small set of selected genes by real-time, quantitative reverse-transcription-polymerase chain reaction (qRT-PCR). This EST collection also provided important new insights into the genetic underpinnings for the biosynthesis and utilization of glycerol and other osmoprotectants, the carotenoid biosynthetic pathway, reactive oxygen-scavenging enzymes, and molecular chaperones (heat shock proteins) not described previously for D. salina. EST discovery also revealed the existence of RNA interference and signaling pathways associated with osmotic stress adaptation. The unknown ESTs described here provide a rich resource for the identification of novel genes associated with the mechanistic basis of salinity stress tolerance and other stress-adaptive traits.
单细胞、耐盐、绿色藻类杜氏盐藻（绿藻门）具有独特的适应和生长能力，能在从约 0.05 到 5.5M 的广泛盐度条件下生长。为了更好地理解其耐盐性的分子基础，构建了一个来自适应 2.5M NaCl 的杜氏盐藻细胞的 cDNA 文库，该文库在 3.4M NaCl 下盐冲击 5 小时，并用于生成表达序列标签 (EST) 数据库。从代表 1401 个独特转录本的 2831 个克隆中获得了 EST。将 EST 与蛋白质数据库进行比较后，为 1901 个（67.2%）EST 分配了推定功能。另外 154 个（5.4%）EST 与功能不明的已知序列具有显著相似性，776 个（27.4%）与已知序列没有相似性。对于那些可以进行功能分配的杜氏盐藻 EST，最大的功能类别包括蛋白质合成（35.7%）、能量（光合作用）（21.4%）、初级代谢（13.8%）和蛋白质命运（6.8%）。在蛋白质合成类别中，绝大多数 EST（80.3%）编码核糖体蛋白，代表约 82 个细胞溶质核糖体亚基中的 95%，表明杜氏盐藻在蛋白质合成的生产和维持上投入了大量资源。通过实时定量逆转录聚合酶链反应 (qRT-PCR) 验证了在一小部分选定基因中，盐冲击后 mRNA 表达增加。该 EST 集还为甘油和其他渗透保护剂的生物合成和利用、类胡萝卜素生物合成途径、活性氧清除酶以及分子伴侣（热休克蛋白）的遗传基础提供了重要的新见解，这些在以前的杜氏盐藻中没有描述过。EST 发现还揭示了与渗透胁迫适应相关的 RNA 干扰和信号通路的存在。这里描述的未知 EST 为鉴定与耐盐性和其他应激适应性状的机制基础相关的新基因提供了丰富的资源。
