Mao Luo

The development dynamics of the maize root transcriptome responsive to heavy metal Pb pollution

Lead (Pb), as a heavy metal element, has become the most important metal pollutant of the environment. With allocating a relatively higher proportion of its biomass in roots, maize could be a potential important model to study the phytoremediation of Pb-contaminated soil. Here we analyzed the maize root transcriptome of inbred lines 9782 under heavy metal lead (Pb) pollution, which was identified as a non-hyperaccumulator for Pb in roots. In the present study, more than 98 millions reads were mapped to define gene structure and detect polymorphism, thereby to qualify transcript abundance along roots development under Pb treatment. A total of 17,707, 17,440, 16,998 and 16,586 genes were identified in maize roots at four developmental stages (0, 12 h, 24 h and 48 h) respectively and 2,825, 2,626, 2161 and 2260 stage-specifically expressed genes were also identified respectively. In addition, based on our RNA-Seq data, transcriptomic changes during maize root development responsive to Pb were investigated. A total of 384 differentially expressed genes (DEGs) (log2Ratio ≥ 1, FDR ≤ 0.001) were identified, of which, 36 genes with significant alteration in expression were detected in four developmental stages; 12 DEGs were randomly selected and successful validated by qRT-PCR. Additionally, many transcription factor families might act as the important regulators at different developmental stages, such as bZIP, ERF and GARP et al. These results will expand our understanding of the complex molecular and cellular events in maize root development and provide a foundation for future study on root development in maize under heavy metal pollution and other cereal crops.

MiR393-targeted TIR1-like (F-box) gene in response to inoculation to R. Solani in Zea mays

AbstractMicroRNAs (miRNAs) are a class of small non-coding RNAs that negatively regulate special target mRNAs at the post-transcriptional level by directing target mRNA cleavage or translational inhibition. Plant miRNAs regulate gene expression mainly by guiding cleavage of target mRNAs and subsequently play important roles in diverse developmental processes, nutrient homeostasis and responses to biotic and abiotic stresses. MiRNA393 plays important and diverse roles in defense against bacterial pathogens by negatively targeting transport inhibitor response 1 (TIR1) in plant development. It will be essential for understanding complex feedback regulations in the development pathway by unraveling the miR393 network in a temporal and spatial manner. Here, we report that Zma-miR393b down-regulates its putative target TIR1-like (F-box) gene by guiding the cleavage of their mRNAs in development of leaf sheaths in response to R. Solani infection, Zma-miR393b and its putative target gene TIR1 were confirmed through Q-PCR and the spatial expression of Zma-miR393b was further analyzed by in situ hybridization. These findings suggested that, as a negative feedback regulation of TIR1-like (F-box) gene, Zma-miR393b plays an important role in defense against R. Solani infection.

The role of miR319 in plant development regulation

MicroRNAs (miRNAs) are an extensive class of endogenous, non-coding, short (21~25 nt) RNA molecules, which regulate expression of target genes through miRNA-guided cleavage or translational repression of mRNAs. Plant miRNAs are involved in all aspects of regulation of plant growth and development. The miR319 was shown to regulate TCPs transcription factor controlling the fate of plant organ growth such as leaves and flowers and was involved in regulating part of hormone biosynthesis and signal transduction pathways. Thus, they play a key biochemical function in plant organs development. This review focused on the key roles of miR319 in regulation of the morphogenesis, development, and senescence of plant organs such as leaves and flowers.

Identification and characterization of differentially expressed microRNAs in response to Rhizoctonia solani in maize

AbstractMicroRNAs (miRNAs) are a set of small, non-coding RNAs that negatively and post-transcriptionally mediate their respective target mRNAs by directing the target mRNA cleavage or translational repression. Plant miRNAs have been involved in developmental processes and adaption to biotic and abiotic stresses in their environment. The banded leaf and sheath blight (BLSB) caused by Rhizoctonia solani is extremely harmful to maize. To investigate the functions of miRNAs under R. solani inoculation, miRNA expression in R. solani infected maize (Zea mays L.) was profiled using deep sequencing. In total, 41 significantly differentially expressed known miRNAs and 39 novel R. solani-responsive miRNAs were identified, of which 9 identified miRNAs were further validated by qRT-PCR, and 2 important miRNAs were analyzed by in situ hybridization. Target genes were also predicted for these R. solani-responsive miRNAs; most of these putative target genes encoded transcription factors and proteins associated with metabolic processes or stress responses. In addition, the mRNA expression levels of several target genes that negatively correlated with the levels of corresponding miRNAs under R. solani inoculation were validated by qRT-PCR. These findings hypothesized that these miRNAs play an important role in R. solani resistance in maize, highlighting novel molecular mechanisms of R. solani resistance in plants.

A putative pathogen-resistant regulatory pathway between MicroRNAs and candidate target genes in maize

MicroRNAs (miRNAs) are a family of small non-coding RNAs that, in most cases, negatively regulate gene expression at the post-transcriptional level. Plant miRNAs have been implicated in developmental processes and adaptation to environmental stress including biotic and abiotic stresses. Here, we report a comprehensive analysis of miRNAs and associated target genes under banded leaf and sheath blight (BLSB) stress caused by R. solani in maize. Eight differentially expressed miRNAs were randomly selected from deep sequencing results and validated by qRT-PCR together with their putative target genes, most of which are transcription factors as well as metabolic genes involved in auxin signaling. The results revealed that majorities of the analyzed miRNAs show an inverse correlation with their corresponding predicted target genes. In addition, a putative regulatory network of miRNAs-mRNAs responsive to R. solani was constructed. This study provides insight into the regulatory functions of miRNAs, thereby expanding our knowledge of the molecular mechanisms of pathogen resistance.