Preliminary Study On The Mechanism Of Ethylene-dependent Tulip Petals Senescence

Tulipa（Tulipa gesneriana L.）is one of the most ornamental bulbous flowers in the world.The extension of flowering period can bring huge economic benefits to tulip growers,and understand the mechanism of action of ethylene in the aging process of tulip petals.The senescence of tulip petals is instructive.In this paper,the flowering lengths of different varieties of tulips were screened,and the varieties with the biggest difference between the two white periods of’White Prince’and’American Dream’were used as experimental materials,and the phenotype,physiological and biochemical level and primary metabolites of flower petals were compared and analyzed.Combined with the transcriptome level and functional gene verification,the molecular mechanism of ethylene-regulated tulip senescence was systematically analyzed.The main conclusions are as follows:1.There is a significant difference in the length of flowering between tulip varieties.A statistical analysis of the length of flowering of 37 tulip varieties collected in the laboratory showed that there were significant differences in the length of flowering between varieties.The white prince had the longest flowering period of more than 20 days;the‘American Dream’flowering period was as short as 7 days.2.Comparative analysis of physiological and biochemical levels during flower senescence.The senescence of tulip petals is accompanied by wilting,water loss and fading.The water content of the petals gradually decreased with the senescence of the petals,and the conductivity gradually increased.At the same time,the chlorophyll content of the petals also changed significantly,and the redox reaction also participated in the senescence process of the petals,H₂O₂ and MDA content gradually increased,POD and CAT activity also shows an upward trend.3.Primary metabolites are involved in the senescence of tulip petals.The results of GC-TOF-MS analysis showed that amino acids,organic acids and primary metabolites of sugars and sugar alcohols changed significantly during the senescence of petals.Among them,serine,glycine,proline,and malic acid and glutamic acid showed an upward trend;while aspartic acid and palmitic acid showed a downward trend.4.Ethylene content and ethylene-related genes changed significantly during the senescence of petals.Exogenous ethylene 1.5g/L treatment of tulip cut flowers can significantly promote the senescence of tulip petals,and the ethylene inhibitor 1-MCP can extend the vase insertion period of tulip cut flowers.The endogenous ethylene content increases as the petals age.The results of real-time PCR showed that the expression levels of some genes involved in ethylene synthesis and signal transduction were significantly increased in the senescent petals.5.Functional analysis of genes involving in ethylene biosynthesis.Four Tg ACO genes and two Tg ACS genes were cloned from two different varieties.Sequence analysis showed that these two genes showed high homology to homologous genes in lily.Overexpression of Tg ACO or Tg ACS in tobacco resulted in a premature aging phenotype,and silencing of endogenous Tg ACO or Tg ACS by virus-mediated transient silencing experiments delayed the senescence of tulip petals.