Cell Wall Enzymes in Zygnema circumcarinatum UTEX 1559 Respond to Osmotic Stress in a Plant-Like Fashion
Cell Wall Enzymes in Zygnema circumcarinatum UTEX 1559 Respond to Osmotic Stress in a Plant-Like Fashion
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DOI：
10.3389/fpls.2019.00732
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发表时间：
2019-06-07
影响因子：
5.6
通讯作者：
Yin, Yanbin
中科院分区：
文献类型：
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作者：
Fitzek, Elisabeth;Orton, Lauren;Yin, Yanbin
先前对轮藻绿色藻类（CGA）基因组和特定蛋白质家族转录组的分析表明，许多陆地植物特征已经在CGA中进化。在这项研究中，我们已经测序和组装的转录组的Zygnema circumcarinatum UTEX 1559，并结合其预测的蛋白质序列与其他13个物种[5个胚胎植物（Emb），8轮藻（Cha），和两个绿藻（Chl）作为外群]进行全面的比较基因组学分析。14个物种的25，485个正向同源基因簇（OGC，相当于蛋白质家族）被分为9个OGC组。例如，Cha+Emb组包含在Cha和Emb中发现的4，174个OGC，但不包含Chl物种，代表在Cha和Emb的共同祖先中进化的蛋白质家族。对不同的OGC组进行基因本体（GO）富集分析，以Chl+Cha+Emb组（包括Chl和Cha和Emb中发现的5，031个OGC）作为对照。有趣的是，Cha+Emb组中20个最丰富的GO术语中有9个是细胞壁相关的，例如涉及纤维素、果胶、木质素和木葡聚糖的生物过程。此外，选择三个糖基转移酶家族（GT 2、8、43）进行深入的系统发育分析，这证实了它们在UTEX 1559中的存在。更重要的是，在不同的CGA组中，只有接合藻具有陆地植物纤维素合酶（CesA）直系同源物，而其他轮藻CesA形成CGA特异性CesA样（Csl）亚家族（可能也携带纤维素合成活性）。对UTEX 1559中选定的GT家族基因进行定量实时PCR实验。在渗透胁迫处理后，发现GT2家族基因ZcCesA、ZcCslC和ZcCslA样（分别可能是甘露聚糖酶和木葡聚糖糖苷酶）以及GT8家族基因（可能是果胶糖苷酶）的表达显著升高。这些结果表明，UTEX 1559细胞壁多糖合成相关基因对渗透胁迫的反应与陆生植物相似。
Previous analysis of charophyte green algal (CGA) genomes and transcriptomes for specific protein families revealed that numerous land plant characteristics had already evolved in CGA. In this study, we have sequenced and assembled the transcriptome of Zygnema circumcarinatum UTEX 1559, and combined its predicted protein sequences with those of 13 additional species [five embryophytes (Emb), eight charophytes (Cha), and two chlorophytes (Chl) as the outgroup] for a comprehensive comparative genomics analysis. In total 25,485 orthologous gene clusters (OGCs, equivalent to protein families) of the 14 species were classified into nine OGC groups. For example, the Cha+Emb group contains 4,174 OGCs found in both Cha and Emb but not Chl species, representing protein families that have evolved in the common ancestor of Cha and Emb. Different OGC groups were subjected to a Gene Ontology (GO) enrichment analysis with the Chl+Cha+Emb group (including 5,031 OGCs found in Chl and Cha and Emb) as the control. Interestingly, nine of the 20 top enriched GO terms in the Cha+Emb group are cell wall-related, such as biological processes involving celluloses, pectins, lignins, and xyloglucans. Furthermore, three glycosyltransferase families (GT2, 8, 43) were selected for in-depth phylogenetic analyses, which confirmed their presence in UTEX 1559. More importantly, of different CGA groups, only Zygnematophyceae has land plant cellulose synthase (CesA) orthologs, while other charophyte CesAs form a CGA-specific CesA-like (Csl) subfamily (likely also carries cellulose synthesis activity). Quantitative real-time-PCR experiments were performed on selected GT family genes in UTEX 1559. After osmotic stress treatment, significantly elevated expression was found for GT2 family genes ZcCesA, ZcCslC and ZcCslA-like (possibly mannan and xyloglucan synthases, respectively), as well as for GT8 family genes (possibly pectin synthases). All these suggest that the UTEX 1559 cell wall polysaccharide synthesis-related genes respond to osmotic stress in a manner that is similar to land plants.