Sweetpotato (Ipomoea batatas. L) is an important food crop, harvested for its nutrient-rich tuberous roots. Drought and salt stresses are two major factors limiting the sweetpotato production. Since microRNAs (miRNAs) are well known to play crucial roles in regulation of plant stress responses, quantitative profiling of miRNA expression under stress conditions will facilitate identification and genetic manipulation of novel miRNAs to improve stress tolerance. Real-time quantitative reverse transcription PCR (qRT-PCR) is a commonly used tool for this purpose, but not without challenges. Although stem-loop and poly(A)-tail modified qRT-PCR methods were developed for characterizing miRNA expression, accurate profiling of miRNAs is still difficult in many plant species because of a lack of reliable reference genes for normalizing miRNA transcripts. To identify reference genes that are suitable for normalizing miRNA expression in sweetpotato, the expression stability of eight candidate miRNAs and two commonly used reference genes were tested in 96 samples involving four tissues and two cultivars under drought and salt stress treatments. Data analysis using the geNorm, NormFinder and Bestkeeper algorithms demonstrated that miRn60, miR482, and their combination were reliable references. We further validated the reference genes by expression analysis of the well-characterized miR319 and miR156 that regulate drought and salt stress responses, respectively. The reference genes identified in this study will facilitate future miRNA analysis under abiotic stress conditions in sweetpotato.

甘薯（Ipomoea batatas。L）是重要的粮食作物，其营养丰富的块根根得以收获。干旱和盐胁迫是限制甘薯产量的两个主要因素。由于众所周知，microRNA（miRNA）在调节植物胁迫反应中起关键作用，因此在胁迫条件下对miRNA表达进行定量分析将有助于鉴定和基因操纵新型miRNA，以提高胁迫耐受性。实时定量逆转录PCR（qRT-PCR）是用于此目的的常用工具，但并非没有挑战。尽管开发了用于修饰miRNA表达特征的茎环和poly（A）尾修饰qRT-PCR方法，但由于缺乏可靠的参考基因来标准化miRNA转录本，因此在许多植物物种中仍然难以对miRNA进行准确的分析。为了鉴定适合标准化甜薯中miRNA表达的参考基因，在干旱和盐胁迫处理下，在涉及四个组织和两个品种的96个样品中测试了八种候选miRNA和两种常用参考基因​​的表达稳定性。使用geNorm，NormFinder和Bestkeeper算法进行的数据分析表明miRn60，miR482及其组合是可靠的参考。我们通过分别表征干旱和盐胁迫响应的特征明确的miR319和miR1 56的表达分析进一步验证了参考基因。在这项研究中确定的参考基因将有助于将来在甘薯非生物胁迫条件下进行miRNA分析。