2018 ASHS Annual Conference

Cai-Zhong Jiang^1,2, Hong Wang^2,3, XiaoXiao Chang², Jing Lin³, Youhong Chang³, Jen-Chih Chen², Michael S. Reid²

¹Crops Pathology and Genetics Research Unit, United States Department of Agriculture, Agricultural Research Service, Davis, California 95616, USA

²Department of Plant Sciences, University of California, Davis, Davis, CA 95616, USA

³Institute of Pomology/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China

Abstract

Genetic regulatory mechanisms that control natural flower senescence in petunia are not well understood. To identify key genes and pathways that regulate the process, we conducted a transcriptome analysis in petunia corolla at four developmental stages, including fully opened corolla without anther dehiscence (D0), two days after anthesis (2 DAA, fully expanded, D2), 4 DAA with initial signs of senescence (D4), and 7 DAA with wilting (D7). We identified large numbers of differentially expressed genes (DEGs), including 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 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.