Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, ON, Canada.
Fungal Biol. 2012 Apr;116(4):478-88. doi: 10.1016/j.funbio.2012.01.007. Epub 2012 Feb 1.
Feruloyl esterases can liberate ferulic acid (FA) from plant cell wall polymers. They are expressed by plant pathogenic fungi and could play a role in pathogenicity, although this question has not been addressed yet. The fungus Fusarium graminearum is the principal causal agent of fusarium head blight (FHB) and gibberella ear rot (GER), major diseases of wheat, barley, and maize in all temperate regions of the world. The F. graminearum genome contains seven genes with strong homology to feruloyl esterase (FAE) sequences. Phylogenetic analysis showed that these included three type B, three type C, and one type D FAE genes. Expression profiling of the seven FAE genes showed complex regulation patterns unique to each gene. In F. graminearum-infected plant tissues, the FAE genes exhibited host-specific gene expression. On wheat, FAEB1 and FAED1 were strongly expressed while FAEB2, FAEB3, and FAEC1 were expressed at more modest levels. On maize, only FAEB3, FAEC1, and FAED1 were expressed and at low levels. When growing F. graminearum in liquid culture, only FAEB1 and FAEC1 were expressed. Both genes were induced by a small group of related aromatic compounds including FA, caffeic acid, and p-coumaric acid. FAEB1 was induced by xylose, while repressed by glucose and galactose. FAEC1 was constitutively expressed at low levels in the presence of those sugars. Expression of the other five FAE genes was not detected in the culture conditions used. To determine if FAE genes were important for pathogenicity of F. graminearum, mutant strains inactivated for faeB1∆, faeD1∆ or both genes were constructed and tested on wheat plants. No statistically significant change in pathogenicity and no compensatory expression of the other FAE genes were observed in the fae gene mutants. Our results show that FAEB1 and FAED1 are not required for pathogenicity of F. graminearum on wheat.
酯酶能够将植物细胞壁聚合物中的阿魏酸（FA）释放出来。它们由植物病原真菌表达，可能在致病性中发挥作用，尽管这个问题尚未得到解决。真菌禾谷镰刀菌是引起小麦赤霉病（FHB）和玉米穗腐病（GER）的主要病原体，这是世界上所有温带地区小麦、大麦和玉米的主要病害。禾谷镰刀菌基因组包含七个与阿魏酸酯酶（FAE）序列具有强同源性的基因。系统发育分析表明，这些基因包括三个 B 型、三个 C 型和一个 D 型 FAE 基因。七个 FAE 基因的表达谱分析显示，每个基因都有独特的复杂调控模式。在感染禾谷镰刀菌的植物组织中，FAE 基因表现出宿主特异性的基因表达。在小麦上，FAEB1 和 FAED1 表达强烈，而 FAEB2、FAEB3 和 FAEC1 表达水平较低。在玉米上，只有 FAEB3、FAEC1 和 FAED1 表达，且表达水平较低。在液体培养中培养禾谷镰刀菌时，只有 FAEB1 和 FAEC1 表达。这两个基因都被一小群相关芳香族化合物诱导，包括 FA、咖啡酸和对香豆酸。FAEB1 被木糖诱导，而被葡萄糖和半乳糖抑制。在这些糖存在的情况下，FAEC1 以低水平组成性表达。在使用的培养条件下，未检测到其他五个 FAE 基因的表达。为了确定 FAE 基因是否对禾谷镰刀菌的致病性很重要，构建了 faeB1∆、faeD1∆或这两个基因失活的突变株，并在小麦植株上进行了测试。在 fae 基因突变体中，致病性没有明显变化，也没有观察到其他 FAE 基因的补偿表达。我们的结果表明，FAEB1 和 FAED1 不是禾谷镰刀菌在小麦上致病性所必需的。
