Abstract
Grain production of rice (Oryza sativa L.) is a top priority in ensuring food security for human beings. One of the approaches to increase yield is to delay leaf senescence and to extend the available time for photosynthesis. MicroRNAs (miRNAs) are key regulators of aging and cellular senescence in eukaryotes. Here, to help understand their biological role in rice leaf senescence, we report identification of miRNAs and their putative target genes by deep sequencing of six small RNA libraries, six RNA-seq libraries and two degradome libraries from the leaves of two super hybrid rice, Nei-2-You 6 (N2Y6, age-resistant rice) and Liang-You-Pei 9 (LYP9, age-sensitive rice). In total 372 known miRNAs, 162 miRNA candidates and 1145 targets were identified. Compared with the expression of miRNAs in the leaves of LYP9, the numbers of miRNAs up-regulated and down-regulated in the leaves of N2Y6 were 47 and 30 at early stage of grain-filling, 21 and 17 at the middle stage, and 11 and 37 at the late stage, respectively. Six miRNA families, osa-miR159, osa-miR160 osa-miR164, osa-miR167, osa-miR172 and osa-miR1848, targeting the genes encoding APETALA2 (AP2), zinc finger proteins, salicylic acid-induced protein 19 (SIP19), auxin response factors (ARF) and NAC transcription factors, respectively, were found to be involved in leaf senescence through phytohormone signaling pathways. These results provided valuable information for understanding the miRNA-mediated leaf senescence of rice, and offered an important foundation for rice breeding.
Highlights
MicroRNAs are short, single strand and endogenous non-coding small RNAs that negatively regulate gene expressions at post-transcriptional level by repressing gene translation or degrading target mRNAs [1, 2]
The mature miRNA is incorporated in the RNA-induced silencing complex (RISC) with endonuclease AGO and guide the cleavage or translational repression of the target mRNA by complementary basepairing [4]
The mechanism mainly was the interplay between miR394 and its target LCR (LEAF CURLING RESPONSIVENESS), an F-box (SKP1-Cullin/CDC53-F-box) gene, which involved in regulating leaf curlingrelated morphology through auxin [12]
Summary
MicroRNAs (miRNAs) are short, single strand and endogenous non-coding small RNAs (sRNAs) that negatively regulate gene expressions at post-transcriptional level by repressing gene translation or degrading target mRNAs [1, 2]. They are encoded by independent transcriptional units in intergenic regions and transcribed by RNA polymerase II or III to form primary miRNA (pri-miRNA). MiR164 ectopic expression or lack of ORE1 activity promoted longevity of Arabidopsis leaf [10] Another miRNA, miR319, targeting TB1, CYC and PCF (TCP), has crucial function in repressing the onset of senescence. The mechanism mainly was the interplay between miR394 and its target LCR (LEAF CURLING RESPONSIVENESS), an F-box (SKP1-Cullin/CDC53-F-box) gene, which involved in regulating leaf curlingrelated morphology through auxin [12]
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