背景:Physcomitriumpatens提供了绿藻和维管植物之间的进化联系。虽然P.patens的基因组包括所有核心木质素生物合成酶的直向同源物,苔藓中木质素的发生存在很大争议。此外,迄今为止,关于苔藓中木质素酶的信息很少。例如,肉桂醇脱氢酶(CAD)是催化木质素生物合成途径最后一步的关键酶,提出了研究进化过程的理想方法。通过研究CAD在进化中的功能,这项研究将阐明类木质素在土地定殖早期的进化作用。
结果:P.patens中的CAD多基因家族由四个基因组成。PpCADs包含一个保守的富含甘氨酸的结构域,以催化NADPH依赖性还原为其相应的醇,表明PpCADs具有通过生物信息学分析合成单木素的潜力。尽管PpCAD1理论上可以产生木质素,在PpCAD1_OE植物的细胞壁或细胞质中未检测到常规单体。然而,在PpCAD1_OE转化体中促进苯丙素类修饰配子体结构和发育,使叶状体的分布更加稀缺,苔藓群落更加庞大,可能是由于AUX-IAA家族的表达增强。在PpCAD1_OE植物中,至少一种编码木质素生物合成途径中的酶的基因的转录物增加。此外,PpCAD1_OE配子体主要通过增强细胞壁中的苯丙烷类物质来抑制灰霉病菌的攻击,而不是影响防御基因发病相关10(PR10)和PR基因1(NPR1)的转录本。同样,PpCAD1在拟南芥中的异位表达导致木质素含量显着增加,表现出厚实的根,健壮的幼苗,高级开花,和对病原体的有效抗性。
结论:PpCAD出现在多个拷贝中,表明祖先植物的功能差异。PpCAD1催化单寡核苷酸生物合成,与维管植物具有同源功能。尽管没有检测到传统的垄断,PpCAD1_OE配子体中苯丙素类化合物的增加,可能是木质素途径中的中间代谢物,在陆生植物的进化过程中具有保守的功能。结果表明,在征服土地期间,早期非维管植物的木质素酶在茎伸长和对P.patens病原体的抗性中起作用。
BACKGROUND: Physcomitrium patens provides an evolutionary link between green algae and vascular plants. Although the genome of P. patens includes orthologs of all the core lignin biosynthetic enzymes, the occurrence of lignin in moss is very controversial. Besides, little information is available about the lignin enzymes in moss to date. For example, cinnamyl alcohol dehydrogenase (CAD) is a crucial enzyme that catalyzes the last step of the lignin biosynthetic pathway, suggesting an ideal way to study the evolutionary process. By investigating the functions of CAD in evolution, this study will elucidate the evolutionary roles of lignin-like in the early stage of land colonization.
RESULTS: CAD multigene family in P. patens is composed of four genes. The PpCADs contain a conserved glycine-rich domain to catalyze NADPH-dependent reduction to their corresponding alcohols, indicating that PpCADs have the potential to synthesize monolignols by bioinformatics analysis. Even though PpCAD1 could produce lignin in theory, no conventional monomer was detected in the cell wall or cytoplasm of PpCAD1_OE plants. However, the phenylpropanoids were promoted in PpCAD1_OE transformants to modify gametophore architecture and development, making the distribution of phyllids more scarcity and the moss colony more giant, possibly due to the enhanced expression of the AUX-IAA family. The transcripts of at least one gene encoding the enzyme in the lignin biosynthetic pathway were increased in PpCAD1_OE plants. In addition, the PpCAD1_OE gametophore inhibited the Botrytis cinerea assault mainly by enhanced phenylpropanoids in the cell wall instead of influencing transcripts of defense genes pathogenesis-related 10 (PR10) and nonexpresser of PR genes 1 (NPR1). Likewise, ectopic expression of PpCAD1 in Arabidopsis led to a significant increase in lignin content, exhibiting chunky roots, robust seedlings, advanced flowering, and efficient resistance against pathogens.
CONCLUSIONS: PpCAD occurs in more than one copy, suggesting functional divergence in the ancestral plant. PpCAD1 catalyzes monolignol biosynthesis and has homologous functions with vascular plants. Despite no detected conventional monolignol, the increased phenylpropanoids in the PpCAD1_OE gametophore, possibly intermediate metabolites in the lignin pathway, had conserved functions during the evolution of terrestrial plants. The results inferred that the lignin enzyme of the early non-vascular plant played roles in stem elongation and resistance against pathogens of P. patens during the conquest of land.