Aravind Jayaraman, Rinku Sharma, Pooja Banduni, Shikha Mittal, Kaliyugam Shiriga, Mallikarjuna Mallana Gowdra, Kumar Arun, Rao Atmakuri Ramakrishna, Nepolean Thirunavukkarasu
Division of Genetics, Indian Agricultural Research InstituteNew Delhi, India.
Division of Germplasm Conservation, National Bureau of Plant Genetic ResourcesNew Delhi, India.
Front Plant Sci. 2017 Jun 2;8:941. doi: 10.3389/fpls.2017.00941. eCollection 2017.
MicroRNA-mediated gene regulation plays a crucial role in controlling drought tolerance. In the present investigation, 13 drought-associated miRNA families consisting of 65 members and regulating 42 unique target mRNAs were identified from drought-associated microarray expression data in maize and were subjected to structural and functional characterization. The largest number of members (14) was found in the zma-miR166 and zma-miR395 families, with several targets. However, zma-miR160, zma-miR390, zma-miR393, and zma-miR2275 each showed a single target. Twenty-three major drought-responsive -regulatory elements were found in the upstream regions of miRNAs. Many drought-related transcription factors, such as GAMYB, HD-Zip III, and NAC, were associated with the target mRNAs. Furthermore, two contrasting subtropical maize genotypes (tolerant: HKI-1532 and sensitive: V-372) were used to understand the miRNA-assisted regulation of target mRNA under drought stress. Approximately 35 and 31% of miRNAs were up-regulated in HKI-1532 and V-372, respectively. The up-regulation of target mRNAs was as high as 14.2% in HKI-1532 but was only 2.38% in V-372. The expression patterns of miRNA-target mRNA pairs were classified into four different types: Type I- up-regulation, Type II- down-regulation, Type III- neutral regulation, and Type IV- opposite regulation. HKI-1532 displayed 46 Type I, 13 Type II, and 23 Type III patterns, whereas V-372 had mostly Type IV interactions (151). A low level of negative regulations of miRNA associated with a higher level of mRNA activity in the tolerant genotype helped to maintain crucial biological functions such as ABA signaling, the auxin response pathway, the light-responsive pathway and endosperm expression under stress conditions, thereby leading to drought tolerance. Our study identified candidate miRNAs and mRNAs operating in important pathways under drought stress conditions, and these candidates will be useful in the development of drought-tolerant maize hybrids.
微小RNA介导的基因调控在控制耐旱性方面起着至关重要的作用。在本研究中，从玉米干旱相关的微阵列表达数据中鉴定出13个与干旱相关的微小RNA家族，由65个成员组成，调控42个独特的靶标信使核糖核酸，并对其进行了结构和功能表征。在zma-miR166和zma-miR395家族中发现的成员数量最多（14个），有多个靶标。然而，zma-miR160、zma-miR390、zma-miR393和zma-miR2275每个都显示出单一靶标。在微小RNA的上游区域发现了23个主要的干旱响应调控元件。许多与干旱相关的转录因子，如GAMYB、HD-Zip III和NAC，与靶标信使核糖核酸相关。此外，使用了两种对比的亚热带玉米基因型（耐旱型：HKI-1532和敏感型：V-372）来了解干旱胁迫下微小RNA对靶标信使核糖核酸的辅助调控。在HKI-1532和V-372中，分别约有35%和31%的微小RNA上调。靶标信使核糖核酸的上调在HKI-1532中高达14.2%，但在V-372中仅为2.38%。微小RNA-靶标信使核糖核酸对的表达模式分为四种不同类型：I型-上调、II型-下调、III型-中性调控和IV型-相反调控。HKI-1532表现出46种I型、13种II型和23种III型模式，而V-372大多具有IV型相互作用（151种）。在耐旱基因型中，与较高水平的信使核糖核酸活性相关的微小RNA的低水平负调控有助于在胁迫条件下维持关键的生物学功能，如脱落酸信号传导、生长素反应途径、光反应途径和胚乳表达，从而导致耐旱性。我们的研究确定了在干旱胁迫条件下在重要途径中起作用的候选微小RNA和信使核糖核酸，这些候选物将有助于耐旱玉米杂交种的培育。
