Plant Metabolic Engineering Laboratory, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India.
BMC Genomics. 2013 Sep 23;14:647. doi: 10.1186/1471-2164-14-647.
Drought tolerance is an attribute maintained in plants by cross-talk between multiple and cascading metabolic pathways. Without a sequenced genome available for horse gram, it is difficult to comprehend such complex networks and intercalated genes associated with drought tolerance of horse gram (Macrotyloma uniflorum). Therefore, de novo transcriptome discovery and associated analyses was done for this highly drought tolerant yet under exploited legume to decipher its genetic makeup.
Eight samples comprising of shoot and root tissues of two horse gram genotypes (drought-sensitive; M-191 and drought-tolerant; M-249) were used for comparison under control and polyethylene glycol-induced drought stress conditions. Using Illumina sequencing technology, a total of 229,297,896 paired end read pairs were generated and utilized for de novo assembly of horse gram. Significant BLAST hits were obtained for 26,045 transcripts while, 3,558 transcripts had no hits but contained important conserved domains. A total of 21,887 unigenes were identified. SSRs containing sequences covered 16.25% of the transcriptome with predominant tri- and mono-nucleotides (43%). The total GC content of the transcriptome was found to be 43.44%. Under Gene Ontology response to stimulus, DNA binding and catalytic activity was highly expressed during drought stress conditions. Serine/threonine protein kinase was found to dominate in Enzyme Classification while pathways belonging to ribosome metabolism followed by plant pathogen interaction and plant hormone signal transduction were predominant in Kyoto Encyclopedia of Genes and Genomes analysis. Independent search on plant metabolic network pathways suggested valine degradation, gluconeogenesis and purine nucleotide degradation to be highly influenced under drought stress in horse gram. Transcription factors belonging to NAC, MYB-related, and WRKY families were found highly represented under drought stress. qRT-PCR validated the expression profile for 9 out of 10 genes analyzed in response to drought stress.
De novo transcriptome discovery and analysis has generated enormous information over horse gram genomics. The genes and pathways identified suggest efficient regulation leading to active adaptation as a basal defense response against drought stress by horse gram. The knowledge generated can be further utilized for exploring other underexploited plants for stress responsive genes and improving plant tolerance.
耐旱性是植物通过多个级联代谢途径之间的交流而保持的一种特性。由于马豆没有测序的基因组，因此很难理解与马豆耐旱性相关的这种复杂网络和插入基因。因此，对这种高度耐旱但尚未开发的豆类进行从头转录组发现和相关分析，以破译其遗传组成。
在对照和聚乙二醇诱导的干旱胁迫条件下，使用两种马豆基因型（耐旱性敏感；M-191 和耐旱性敏感；M-249）的 8 个样本的茎和根组织进行了比较。使用 Illumina 测序技术，共产生了 229,297,896 对末端读对，并用于马豆的从头组装。26,045 个转录本获得了显著的 BLAST 命中，而 3,558 个转录本没有命中，但包含重要的保守结构域。总共鉴定了 21,887 个非冗余基因。含有序列的 SSR 覆盖了转录组的 16.25%，主要是三核苷酸和单核苷酸（43%）。转录组的总 GC 含量为 43.44%。在基因本体论对刺激的反应中，干旱胁迫条件下 DNA 结合和催化活性表达较高。丝氨酸/苏氨酸蛋白激酶在酶分类中占主导地位，而核糖体代谢、植物病原体相互作用和植物激素信号转导途径在京都基因与基因组百科全书分析中占主导地位。对植物代谢网络途径的独立搜索表明，马豆在干旱胁迫下，缬氨酸降解、糖异生和嘌呤核苷酸降解受到强烈影响。在干旱胁迫下，属于 NAC、MYB 相关和 WRKY 家族的转录因子表达水平较高。qRT-PCR 验证了 10 个分析基因中 9 个对干旱胁迫的表达谱。
从头转录组发现和分析为马豆基因组学生成了大量信息。鉴定的基因和途径表明，马豆通过有效的调节来积极适应干旱胁迫，作为对干旱胁迫的基本防御反应。所产生的知识可以进一步用于探索其他未充分开发的植物中的应激响应基因，以提高植物的耐受性。
