Transcriptomic analysis reveals ethylene’s regulation involved in adventitious roots formation in lotus (Nelumbo nucifera Gaertn.)

Abstract

Adventitious roots (ARs) play an irreplaceable role in the uptake of water and nutrients due to under-developed principle root in plants. The process of ARs formation is affected by plant hormone. In this study, by employing High-Throughout Tag-sequencing Technique and ELISA method, we analyzed of the transcriptome and indole-3-acetic acid (IAA) content to monitor the changes of metabolism regulated by ethylene signaling in lotus. Exogenous application of ethephon (ethylene precursor) dramatically accelerated ARs development, and while restrained by 1-methylcyclopropene (1-MCP, the ethylene perception inhibitor), indicating the crucial role ethylene in ARs development. Transcriptomic analysis showed that both treatment of ethephon and 1-MCP dramatically altered the expression of numerous genes. In total, transcriptional expressions of 694 genes were induced and 554 genes were suppressed in ETH/CK0 stages compared with MCP/CK0 stages. Most of these up-regulated genes exhibited the one-three folds changes. In ETH/MCP libraries, we found nine and five genes involved in the metabolism or transcriptional responses to ethylene and IAA, and fourteen genes, which were considered to NAC, bHLH, AP2-EREBP, MYB, LOB, bHLH and bZIP families, respectively, exhibited an increase in transcriptional level. In addition, an enhanced mRNA levels of seven genes [1-aminocyclopropane-1-carboxylate oxidase (ACO), leucine-rich repeat receptor, pectinesterase, pyruvate decarboxylase, ethylene oxide synthase, respiratory burst oxidase homolog protein and xyloglucan endotransglucosylase] relevant to ARs formation were detected in was detected in ETH/MCP libraries. Furthermore, we found that IAA content was obviously decreased after applications were detected on ethephon and 1-MCP. However, the decreased IAA level in 1-MCP treatment was more pronounced than that in ethephon treatment, and kept a low level during the whole periods of ARs development. Taken together, our findings provided a comprehensive understanding of ethylene’s regulation during ARs formation in lotus seedlings.