Lignin is a key secondary cell wall chemical constituent, and is both a barrier to biomass utilization and a potential source of bioproducts. The Arabidopsis transcription factors MYB58 and MYB63 have been shown to upregulate gene expression of the general phenylpropanoid and monolignol biosynthetic pathways. The overexpression of these genes also results in dwarfism. The vascular integrity, soluble phenolic profiles, cell wall lignin, and transcriptomes associated with these MYB‐overexpressing lines were characterized. Plants with high expression of MYB58 and MYB63 had increased ectopic lignin and the xylem vessels were regular and open, suggesting that the stunted growth is not associated with loss of vascular conductivity. MYB58 and MYB63 overexpression lines had characteristic soluble phenolic profiles with large amounts of monolignol glucosides and sinapoyl esters, but decreased flavonoids. Because loss of function lac4 lac17 mutants also accumulate monolignol glucosides, we hypothesized that LACCASE overexpression might decrease monolignol glucoside levels in the MYB‐overexpressing plant lines. When laccases related to lignification (LAC4 or LAC17) were co‐overexpressed with MYB63 or MYB58, the dwarf phenotype was rescued. Moreover, the overexpression of either LAC4 or LAC17 led to wild‐type monolignol glucoside levels, as well as wild‐type lignin levels in the rescued plants. Transcriptomes of the rescued double MYB63‐OX/LAC17‐OX overexpression lines showed elevated, but attenuated, expression of the MYB63 gene itself and the direct transcriptional targets of MYB63. Contrasting the dwarfism from overabundant monolignol production with dwarfism from lignin mutants provides insight into some of the proposed mechanisms of lignin modification‐induced dwarfism.

中文翻译：

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异位LACCASE的过表达挽救了高薄荷醇拟南芥植物的矮化。

木质素是关键的二次细胞壁化学成分，既是生物质利用的障碍，也是生物产物的潜在来源。拟南芥转录因子MYB58和MYB63已显示出上调一般苯丙烷和单木酚生物合成途径的基因表达。这些基因的过度表达也会导致侏儒症。表征了这些MYB过表达系相关的血管完整性，可溶性酚类，细胞壁木质素和转录组。高表达MYB58和MYB63的植物异位木质素增加，木质部血管规则且开放，这表明生长受阻与血管传导性降低无关。MYB58和MYB63过表达品系具有特征性的可溶性酚类特征，其中含有大量的单木酚糖苷和芥子酸酯，但类黄酮含量下降。由于功能损失lac4 lac17突变体也积聚了单木酚糖苷，我们假设LACCASE过表达可能会降低MYB过表达植物株中单木酚糖苷的水平。当与木质化相关的漆酶（LAC4或LAC17）与MYB63或MYB58共表达时，矮表型得以拯救。此外，LAC4或LAC17的过表达导致野生型单木酚糖苷水平以及所拯救植物中的野生型木质素水平。挽救的双重MYB63-OX / LAC17-OX过表达株的转录组显示出MYB63基因本身和MYB63的直接转录靶标的表达升高但减弱。将过多的单木香醇生产产生的矮化与木质素突变体产生的矮化进行对比，可以洞悉木质素修饰引起的矮化的一些拟议机制。