Laccases (LACs) are versatile enzymes that catalyze oxidation of a wide range of substrates, thereby functioning in regulation of plant developmental processes and stress responses. However, with a few exceptions, the function of most LACs remains unclear in plants. In this study, we newly identified 4, 12, 22, 26, 27, 28 and 49 LAC genes for Physcomitrella patens , Amborella trichopoda , Zea mays , Ricinus communis , Vitis vinifera , Triticum aestivum and Glycine max , on the basis of exhaustive homologous sequence searches. In these plants, LACs differ greatly in sequence length and physical properties, such as molecular weight and theoretical isoelectric point (pI), but majority of them contain a signal peptide at their N-terminus. The originality of LACs could be traced back to as early as the emergence of moss. Plant LACs are clearly divided into seven distinct classes, where six ancient LACs should be present prior to the divergence of gymnosperms and angiosperms. Functional divergence analysis reveal that functional differentiation should occur among different groups of LACs because of altered selective constraints working on some critical amino acid sites (CAASs) within conserved laccase domains during evolution. Soybean and maize LACs have significantly different exon frequency (6.08 vs 4.82), and they are unevenly distributed and tend to form gene clusters on some chromosomes. Further analysis shows that the expansion of LAC gene family would be due to extensive tandem and chromosomal segmental duplications in the two plant species. Interestingly, ~81.6% and 36.4% of soybean and maize LACs are potential targets of miRNAs, such as miR397a/b, miR408d, or miR528a/b etc. Both soybean and maize LACs are tissue-specifically and developmental-specifically expressed, and are in response to different external abiotic and biotic stressors. These results suggest a diversity of functions of plant LAC genes, which will broaden our understanding and lay solid foundation for further investigating their biological functions in plants.

中文翻译：

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植物漆酶基因功能和表达的进化差异

漆酶 (LAC) 是一种多功能酶，可催化多种底物的氧化，从而在调节植物发育过程和应激反应中发挥作用。然而，除了少数例外，大多数 LAC 在植物中的功能仍不清楚。在本研究中，我们新鉴定了 4、12、22、26、27、28 和 49 个 LAC 基因为 Physcomitrella patens、Amborella trichopoda、Zea mays、Ricinus community、Vitis vinifera、Triticum aestivum 和 Glycine max序列搜索。在这些植物中，LAC 在序列长度和物理特性（例如分子量和理论等电点 (pI)）上有很大差异，但它们中的大多数在 N 端都含有信号肽。LAC的起源最早可以追溯到苔藓的出现。植物 LAC 清楚地分为七个不同的类别，其中在裸子植物和被子植物分化之前应该存在六个古老的 LAC。功能差异分析表明，由于在进化过程中对保守漆酶结构域内的一些关键氨基酸位点 (CAAS) 起作用的选择性约束发生改变，因此不同 LAC 组之间应该发生功能分化。大豆和玉米 LAC 具有显着不同的外显子频率（6.08 vs 4.82），并且它们分布不均并且倾向于在某些染色体上形成基因簇。进一步分析表明 LAC 基因家族的扩展将是由于两种植物物种中广泛的串联和染色体节段重复。有趣的是，约 81.6% 和 36.4% 的大豆和玉米 LAC 是 miRNA 的潜在靶标，例如 miR397a/b、miR408d、或 miR528a/b 等。大豆和玉米 LAC 均具有组织特异性和发育特异性表达，并对不同的外部非生物和生物胁迫做出响应。这些结果表明植物LAC基因功能的多样性，将拓宽我们的认识，为进一步研究其在植物中的生物学功能奠定坚实的基础。