欧洲山杨液泡膜Na+/H+ 反向运输体的性质鉴定

植物液泡膜Na /H 反向运输体可将细胞质中的Na 转运到液泡内储存,以减少胞内Na 的毒性.但木本植物如杨树是否有同样的机制目前还不清楚.以欧洲山杨的愈伤组织为材料,捣碎破碎愈伤组织细胞,经过差速离心和不连续蔗糖梯度离心得到纯化的欧洲山杨液泡微囊.通过液泡V-ATPase建立质子梯度,该液泡能够利用此梯度调控Na 的转运,表明液泡膜上存在Na /H 反向运输体活性(表观米氏常数Km是11.4mmol/L).Na /H 反向运输体的抑制剂——氨氯吡嗪咪能明显抑制转运体的活性.该Na /H 反向运输体也可以转运K ,但亲和能力比Na 低30%.该结果首次证明木本植物的液泡膜上存在Na /H 反向运输体.初步功能研究表明,愈伤组织在盐胁迫条件下,Na /H 反向运输体活性明显下降,提示该机制可能与山杨不耐盐有关.

Characterization of The Na+/H+ Antiporter in Tonoplast Vesicles From Populus tremula. calli

The Na /H antiporter in vacuolar membranes transports Na from the cytoplasm to vacuoles using a pH gradient generated by proton pumps, which could reduce Na toxicity. It is uncertain that whether the woody plants have the same mechanism. Through differential centrifugation and sucrose density gradient centrifugation, tonoplast vesicles were isolated from Populus tremula calli broken by blender. After establishing pH gradient by V-ATPase, Na could dissipate the pH gradient, which indicates that there is Na /H antiporter in the tonoplast vesicles from Populus tremula calli (Km=11.4 mmol/L). Amiloride could inhibit the Na /H antiporter activity. The antiporter could transport Na and K , the affinity for Na is higher. Salt stress decreased Km and Vmax.