Transcriptome profiling reveals regulatory mechanisms underlying corolla senescence in petunia

Hong Wang,Michael S Reid,Xiaoxiao Chang,Jen-Chih Chen,Cai-Zhong Jiang,Jing Lin,Youhong Chang

doi:10.1038/s41438-018-0018-1

Abstract

The genetic regulatory mechanisms that govern natural corolla senescence in petunia are not well understood. To identify key genes and pathways that regulate the process, we performed a transcriptome analysis in petunia corolla at four developmental stages, including corolla fully opening without anther dehiscence (D0), corolla expansion, 2 days after anthesis (D2), corolla with initial signs of senescence (D4), and wilting corolla (D7). We identified large numbers of differentially expressed genes (DEGs), ranging from 4626 between the transition from D0 and D2, 1116 between D2 and D4, a transition to the onset of flower senescence, and 327 between D4 and D7, a developmental stage representing flower senescence. KEGG analysis showed that the auxin- and ethylene-related hormone biosynthesis and signaling transduction pathways were significantly activated during the flower development and highly upregulated at onset of flower senescence. Ethylene emission was detected at the D2 to D4 transition, followed by a large eruption at the D4 to D7 transition. Furthermore, large numbers of transcription factors (TFs) were activated over the course of senescence. Functional analysis by virus-induced gene silencing (VIGS) experiments demonstrated that inhibition of the expression of TFs, such as ethylene-related ERF, auxin-related ARF, bHLH, HB, and MADS-box, significantly extended or shortened flower longevity. Our data suggest that hormonal interaction between auxin and ethylene may play critical regulatory roles in the onset of natural corolla senescence in petunia.

Highlights

Petal senescence is the irreversible and final stage of floral differentiation and development, associated with dynamic alterations once a flower has been successfully pollinated[1,2]
Corolla limbs were collected on day 0 (D0), when flowers were open but before the anthers dehisced, day 2 after anthesis (D2, corolla were fully expanded), day 4 (D4, corolla displayed a wilting sign at the tip edge, considered as the onset of flower senescence), and day 7 (D7, corolla showed wilting)
Floral senescence and ET production Flowers that were fully opened but anthers not yet dehisced were marked as D0

Summary

Introduction

Petal senescence is the irreversible and final stage of floral differentiation and development, associated with dynamic alterations once a flower has been successfully pollinated[1,2]. It is not clear how the process is regulated genetically. In ethylene (ET)-sensitive flowers, the first sign of visible senescence is accompanied by a transient and sudden rise of ET production[4] Other hormones such as cytokinin (CK)[5], abscisic acid (ABA), auxin[6], gibberellic acid (GA)[7], and jasmonic acid (JA)[8] are involved in ET-sensitive petal senescence. ABA accelerates petal senescence[9]

Methods

Results

Conclusion