Mir Derikvand Mohammad, Sierra Jimmy Berrio, Ruel Katia, Pollet Brigitte, Do Cao-Trung, Thévenin Johanne, Buffard Dominique, Jouanin Lise, Lapierre Catherine
Biologie Cellulaire, INRA, Versailles Cedex, France.
Planta. 2008 Apr;227(5):943-56. doi: 10.1007/s00425-007-0669-x. Epub 2007 Nov 29.
Cinnamoyl-CoA reductase 1 (CCR1, gene At1g15950) is the main CCR isoform implied in the constitutive lignification of Arabidopsis thaliana. In this work, we have identified and characterized two new knockout mutants for CCR1. Both have a dwarf phenotype and a delayed senescence. At complete maturity, their inflorescence stems display a 25-35% decreased lignin level, some alterations in lignin structure with a higher frequency of resistant interunit bonds and a higher content in cell wall-bound ferulic esters. Ferulic acid-coniferyl alcohol ether dimers were found for the first time in dicot cell walls and in similar levels in wild-type and mutant plants. The expression of CCR2, a CCR gene usually involved in plant defense, was increased in the mutants and could account for the biosynthesis of lignins in the CCR1-knockout plants. Mutant plantlets have three to four-times less sinapoyl malate (SM) than controls and accumulate some feruloyl malate. The same compositional changes occurred in the rosette leaves of greenhouse-grown plants. By contrast and relative to the control, their stems accumulated unusually high levels of both SM and feruloyl malate as well as more kaempferol glycosides. These findings suggest that, in their hypolignified stems, the mutant plants would avoid the feruloyl-CoA accumulation by its redirection to cell wall-bound ferulate esters, to feruloyl malate and to SM. The formation of feruloyl malate to an extent far exceeding the levels reported so far indicates that ferulic acid is a potential substrate for the enzymes involved in SM biosynthesis and emphasizes the remarkable plasticity of Arabidopsis phenylpropanoid metabolism.
肉桂酰辅酶A还原酶1（CCR1，基因At1g15950）是拟南芥组成型木质化过程中主要的CCR同种型。在这项研究中，我们鉴定并表征了两个新的CCR1基因敲除突变体。这两个突变体均具有矮化表型和衰老延迟的特征。在完全成熟时，它们的花序茎木质素水平降低了25%-35%，木质素结构存在一些改变，抗性单元间键的频率更高，细胞壁结合阿魏酸酯的含量也更高。首次在双子叶植物细胞壁中发现了阿魏酸-松柏醇醚二聚体，野生型和突变体植物中的含量相似。通常参与植物防御的CCR基因CCR2在突变体中的表达增加，这可能解释了CCR1基因敲除植物中木质素的生物合成。突变体幼苗的芥子酰苹果酸（SM）含量比对照少三到四倍，并积累了一些阿魏酰苹果酸。温室种植植物的莲座叶也出现了相同的成分变化。相比之下，相对于对照，它们的茎中异常高水平地积累了SM和阿魏酰苹果酸以及更多的山奈酚糖苷。这些发现表明，在其木质素含量降低的茎中，突变体植物可能通过将阿魏酰辅酶A重定向到细胞壁结合的阿魏酸酯、阿魏酰苹果酸和SM来避免其积累。阿魏酰苹果酸的形成程度远远超过迄今报道的水平，这表明阿魏酸是参与SM生物合成的酶的潜在底物，并强调了拟南芥苯丙烷代谢的显著可塑性。
