Abstract
BackgroundMaize grain yield depends mainly on the photosynthetic efficiency of functional leaves, which is controlled by an array of gene networks and other factors, including environmental conditions. MicroRNAs (miRNAs) are small RNA molecules that play important roles in plant developmental regulation. A few senescence-associated miRNAs (SA-miRNAs) have been identified as important participants in regulating leaf senescence by modulating the expression levels of their target genes.ResultsTo elucidate miRNA roles in leaf senescence and their underlying molecular mechanisms in maize, a stay-green line, Yu87-1, and an early leaf senescence line, Early leaf senescence-1 (ELS-1), were selected as experimental materials for the differential expression of candidate miRNAs. Four small RNA libraries were constructed from ear leaves at 20 and 30 days after pollination and sequenced by Illumina deep sequencing technology. Altogether, 81 miRNAs were detected in both lines. Of these, 16 miRNAs of nine families were differentially expressed between ELS-1 andYu87-1. The phenotypic and chlorophyll content analyses of both lines identified these 16 differentially expressed miRNAs as candidate SA-miRNAs.ConclusionsIn this study, 16 candidate SA-miRNAs of ELS-1 were identified through small RNA deep sequencing technology. Degradome sequencing results indicated that these candidate SA-miRNAs may regulate leaf senescence through their target genes, mainly transcription factors, and potentially control chlorophyll degradation pathways. The results highlight the regulatory roles of miRNAs during leaf senescence in maize.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0755-y) contains supplementary material, which is available to authorized users.
Highlights
Maize grain yield depends mainly on the photosynthetic efficiency of functional leaves, which is controlled by an array of gene networks and other factors, including environmental conditions
Characterization of leaf senescence in two inbred lines To characterize the senescence behavior of early leaf senescence (ELS)-1 and Yu87-1, the phenotypes of ear leaves at 10DAP, 20DAP, 25DAP, and 30DAP were observed in the field
The leaves of inbred line ESL-1 lost their green color during the 20–25 days after pollination (DAP) period, while the leaves of inbred line Yu87-1 stayed green during this stage (Fig. 1)
Summary
Maize grain yield depends mainly on the photosynthetic efficiency of functional leaves, which is controlled by an array of gene networks and other factors, including environmental conditions. A few senescenceassociated miRNAs (SA-miRNAs) have been identified as important participants in regulating leaf senescence by modulating the expression levels of their target genes. Leaf senescence is a major physiological process that affects vegetative and productive developmental processes in plants, and delayed senescence can prolong the leaf life span and increase seed yield [1]. The conversion from leaf maturation to senescence is complex and associated with changes in genome-wide gene expression levels and several senescence-associated genes (SAGs) have been discovered in many plant species [4]. The phytohormone response pathway is important in the leaf senescence regulatory network. NAC members are transcription factors involved in plant leaf senescence [9]. AUX is an negative regulatory factor in leaf senescence, while Auxin Response Factor transcription factors could bind to the promoters of the AUX genes and regulate their
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