Applied Cell Biology

Comparative analysis of miRNA expression under leaf removal conditions reveals the role of IAA in adventitious root formation in lotus (Nelumbo nucifera Gaertn.) seedlings

Liu quan1, Zhao minrong1, Miao minmin1, Li Shuyan2* and Cheng Libao1*

¹School of Horticulture and Plant Protection, Yangzhou University, Jiangsu, P. R. China
²College of Guangling, Yangzhou University, Jiangsu, P. R. China; E-mail: lsydbnd@163.com

Abstract

MicroRNA regulation of targeted gene expression is involved in plant growth and development. In this study, overwater leaf removal (OLR) significantly increased the number of adventitious roots (ARs), which was inhibited upon underwater leaf removal (ULR). Additionally, indole acetic acid (IAA) content was significantly decreased in OLR and ULR after 2 days, whereas OLR IAA content was greater than the control and ULR, after 4 days. Changes in IAA content was highly correlated with the second leaf development. Therefore, miRNA expression of five libraries was analyzed using RNA-sequencing to monitor molecular regulation mechanisms of AR formation in OLR or ULR treatment. We obtained 1.2–1.4 × 10⁷ reads (1.1 × 10⁷ clean reads per library). The total number of miRNAs (18–30 nt) was lesser than 5% of small RNAs. Among these (known and novel), 352, 245, 376, and 434 miRNAs were differentially expressed in the A1/C0, A2/A1, B1/C0, and B2/B1 stages, respectively. Expression profiling analysis showed that these miRNAs were differentially expressed ~-4−4-fold. The associated top 20 enriched pathways were involved in plant hormone signal transduction, and starch and sucrose metabolism in A1/B1 libraries. Expression of 13 miRNAs related to AR development was monitored in the A1/B1 library, among which nine miRNAs (7 upregulated and 2 downregulated) had altered transcription levels. Nine miRNAs were selected for further expression profiling from the C0 to the A1 and B1 stages using qRT-PCR. In a total, miRNAs regulate AR formation by differential expression in OLR and ULR treatments.

Keywords:

lotus, ARs, gene, leaf removal, miRNA