Abstract：
Broussonetia papyrifera, a valuable feed resource, is known for its fast growth, wide adaptability, high protein content and strong selenium enrichment capacity. Selenomethionine (SeMet), the main selenium form in selenium fortification B. papyrifera, is safe for animals and this enhances its nutritional value as a feed resource. However, the molecular mechanisms underlying SeMet synthesis remain unclear. This study identified three homocysteine S-methyltransferase genes from the B. papyrifera genome. The phylogenetic tree demonstrated that BpHMTs were divided into two classes, and BpHMT2 in the Class 2-D subfamily evolved earlier and possesses more fundamental functions. On the basis of the correlation between gene expression levels and selenium content, BpHMT2 was identified as a key candidate gene associated with selenium tolerance. Subcellular localization experiments confirmed the targeting of BpHMT2 in nucleus, cell membrane and chloroplasts. Moreover, three BpHMT2 overexpression Arabidopsis thaliana lines were confirmed to enhance plant selenium tolerance and SeMet accumulation. Overall, our finding provides insights into the molecular mechanisms of selenium metabolism in B. papyrifera, highlighting the potential role of BpHMT2 in SeMet synthesis. This research contributes to our understanding of selenium-enriched feed resources, with increased SeMet content contributing to the improved nutritional value of B. papyrifera as a feed resource.
摘要：
构树,宝贵的饲料资源，以其快速增长而闻名，广泛的适应性，蛋白质含量高,富硒能力强。硒蛋氨酸（SeMet），硒强化中的主要硒形式。对动物来说是安全的，并提高了其作为饲料资源的营养价值。然而,SeMet合成的分子机制尚不清楚.这项研究从B.papyririfera基因组中鉴定了三个同型半胱氨酸S-甲基转移酶基因。系统发育树表明，BpHMTs分为两类，2-D类亚家族中的BpHMT2进化较早，具有更基本的功能。根据基因表达水平与硒含量的相关性,BpHMT2被鉴定为与硒耐受性相关的关键候选基因。亚细胞定位实验证实了BpHMT2在细胞核中的靶向，细胞膜，和叶绿体。此外，三个过表达BpHMT2的拟南芥品系被证实可以增强植物对硒的耐受性和SeMet的积累。总的来说,我们的发现提供了对B.papyrifera中硒代谢的分子机制的见解，强调BpHMT2在SeMet合成中的潜在作用。这项研究有助于我们了解富硒饲料资源，SeMet含量的增加有助于提高B.papyrifera作为饲料资源的营养价值。
