背景:构树是一种具有很高利用价值的经济意义的树木,然而,它的种植往往受到重金属(HM)土壤污染的限制。有效科学的栽培管理,这提高了B.papyrifera的产量和质量,有必要了解其对HM压力的调节机制。
结果:在B.papyrifera中鉴定出12个金属硫蛋白(MT)基因。他们的开放阅读框架范围从186到372bp,编码61至123个氨基酸的蛋白质,分子量在15,473.77和29,546.96Da之间,和理论等电点从5.24到5.32。系统发育分析将这些BpMT分为三个亚类:MT1,MT2和MT3,其中MT2包含七个成员,MT3仅一个。大部分BpMT基因表达受Cd诱导,Mn,Cu,Zn,和脱落酸(ABA)治疗,特别是BpMT2e,BpMT2d,BpMT2c,和BpMT1c,显示出显著的反应,值得进一步研究。表达这些BpMT基因的酵母细胞对Cd的耐受性增强,Mn,Cu,和锌应力与对照细胞相比。带有BpMT1c的酵母,BpMT2e,BpMT2d表现出更高的Cd积累,Cu,Mn,Zn,提示BpMTs对HMs的螯合和结合能力。半胱氨酸(Cys)残基的定点诱变表明,1型BpMT的C域突变导致对HMs的敏感性增加,并减少了酵母细胞中HM的积累;而在2型BpMTs中,N和C结构域对HMs螯合的贡献可能与Cys残基的数量相关。
结论:BpMT基因在响应多种HM胁迫中至关重要,并参与ABA信号传导。BpMTs的富含Cys的结构域对于HM耐受性和螯合是关键的。这项研究为1型和2型植物MTs的结构-功能关系和金属结合能力提供了新的见解,增强我们对它们在植物适应HM胁迫中的作用的理解。
BACKGROUND: Broussonetia papyrifera is an economically significant tree with high utilization value, yet its cultivation is often constrained by soil contamination with heavy metals (HMs). Effective scientific cultivation management, which enhances the yield and quality of B. papyrifera, necessitates an understanding of its regulatory mechanisms in response to HM stress.
RESULTS: Twelve Metallothionein (MT) genes were identified in B. papyrifera. Their open reading frames ranged from 186 to 372 bp, encoding proteins of 61 to 123 amino acids with molecular weights between 15,473.77 and 29,546.96 Da, and theoretical isoelectric points from 5.24 to 5.32. Phylogenetic analysis classified these BpMTs into three subclasses: MT1, MT2, and MT3, with MT2 containing seven members and MT3 only one. The expression of most BpMT genes was inducible by Cd, Mn, Cu, Zn, and abscisic acid (ABA) treatments, particularly BpMT2e, BpMT2d, BpMT2c, and BpMT1c, which showed significant responses and warrant further study. Yeast cells expressing these BpMT genes exhibited enhanced tolerance to Cd, Mn, Cu, and Zn stresses compared to control cells. Yeasts harboring BpMT1c, BpMT2e, and BpMT2d demonstrated higher accumulation of Cd, Cu, Mn, and Zn, suggesting a chelation and binding capacity of BpMTs towards HMs. Site-directed mutagenesis of cysteine (Cys) residues indicated that mutations in the C domain of type 1 BpMT led to increased sensitivity to HMs and reduced HM accumulation in yeast cells; While in type 2 BpMTs, the contribution of N and C domain to HMs\' chelation possibly corelated to the quantity of Cys residues.
CONCLUSIONS: The BpMT genes are crucial in responding to diverse HM stresses and are involved in ABA signaling. The Cys-rich domains of BpMTs are pivotal for HM tolerance and chelation. This study offers new insights into the structure-function relationships and metal-binding capabilities of type-1 and - 2 plant MTs, enhancing our understanding of their roles in plant adaptation to HM stresses.