核盘菌侵染对拟南芥表皮蜡质结构及化学组成的影响

以野生型拟南芥与蜡质突变体cer1、cer4为试验材料,通过研究核盘菌胁迫对拟南芥茎表皮蜡质结构及组分含量的影响,揭示核盘菌侵染与表皮蜡质的关系。扫描电镜结果显示,野生型拟南芥蜡质晶体以垂直于表面的杆状、块状结构为主;突变体cer1晶体类型以水平的松针状、块状结构为主;突变体cer4蜡质晶体以垂直片层结构为主。核盘菌胁迫下,拟南芥蜡质晶体结构及分布形态发生变化。蜡质层结构在核盘菌胁迫下表现为:杆状、松针状蜡质晶体减少—蜡质晶体熔融—表皮"囊状凸起"—表皮膜层破裂。这些结构变化有利于病菌突破角质层屏障而侵入到植株体内。色质谱分析结果显示:与野生型相比,cer1突变体烷、次级醇、酮类显著减少;cer4突变体表现为一级醇含量减少。接种核盘菌后,野生型拟南芥与蜡质突变体一级醇类显著增加(cer1增加不显著);烷类、次级醇类、酮类含量与蜡质总量均显著减少,表明蜡质前体物质在受到核盘菌胁迫后更多地通过酰基还原途径生成一级醇,从而减少了由脱羰基途径所生成的蜡质组分。核盘菌通过改变表皮蜡质晶体结构与化学组分分泌量来促进侵染。

Effects of Sclerotinia sclerotiorum on the morphology and chemical constituents of epicuticular wax in Arabidopsis thaliana stems

Epicuticular waxes form the outermost layer over the membrane and are visible on Arabidopsis inflorescence stem surfaces as a bluish-white colored coating. In the current study, the effects of Sclerotinia sclerotiorum on epicuticular wax morphology and constituents in Arabidopsis thaliana stems were analyzed, aiming to elucidate the relationship between fungal invasion and plant epicuticular wax. Wax mutants cer1 (the contents of alkanes, secondary alcohols, and ketones reduced significantly), cer4 (the contents of primary alcohols reduced significantly), and one wild type of A. thaliana were selected as experimental materials. Scanning electron microscope technology was used to investigate the changes of crystalloid structure. Gas chromatography and mass spectrometry technology was used to measure the amounts of total wax and wax constituents. The results showed that wax morphology of A. thaliana wild type was composed primarily of vertical rods and plates, that of wax mutant cer1 was composed primarily of horizontal needles and plates and the density and size of crystalloids reduced. Wax mutant cer4 had a very high density of vertically oriented (relative to the horizontal cuticle surface) plate-like waxes. The infection of S. sclerotiorum altered the crystalloid morphology of epicuticular wax in stems. The changing pattern of wax crystalloid morphology under S. sclerotiorum infection might be as follows, decrease of "rod crystalloids-fusion of wax crystalloids into epidermis-surface protuberances-epidermis cracks. These changes of wax crystalloid morphology enabled S. sclerotiorum break through the cuticle barrier and infect plant. Infection also altered the secretion amounts of wax constituents. After inoculation with S. sclerotiorum, the content of primary alcohols in wild type and wax mutants increased significantly except cer1, while the content of alkanes, secondary alcohols, ketones and total wax decreased significantly. This suggested that more wax precursors converted to primary alcohol from acyl reduction pathway under S. sclerotiorum stress, resulting a decrease of wax amounts from decarbonylation pathway. The S. sclerotiorum promoted it's penetration to epidermis by altering the crystalloid morphology and constituents of plant epicuticular wax.