Differences in Grain Ultrastructure, Phytochemical and Proteomic Profiles between the Two Contrasting Grain Cd-Accumulation Barley Genotypes

To reveal grain physio-chemical and proteomic differences between two barley genotypes, Zhenong8 and W6nk2 of high- and low- grain-Cd-accumulation, grain profiles of ultrastructure, amino acid and proteins were compared. Results showed that W6nk2 possesses significantly lower protein content, with hordein depicting the greatest genotypic difference, compared with Zhenong8, and lower amino acid contents with especially lower proportion of Glu, Tyr, Phe and Pro. Both scanning and transmission electron microscopy observation declared that the size of A-type starch molecule in W6nk2 was considerably larger than that of Zhenong8. Grains of Zhenong8 exhibited more protein-rich deposits around starch granules, with some A-type granules having surface pits. Seventeen proteins were identified in grains, using 2-DE coupled with mass spectrometry, with higher expression in Zhenong8 than that in W6nk2; including z-type serpin, serpin-Z7 and alpha-amylase/trypsin inhibitor CM, carbohydrate metabolism, protein synthesis and signal transduction related proteins. Twelve proteins were less expressed in Zhenong8 than that in W6nk2; including barley trypsin inhibitor chloroform/methanol-soluble protein (BTI-CMe2.1, BTI-CMe2.2), trypsin inhibitor, dehydroascorbate reductase (DHAR), pericentrin, dynein heavy chain and some antiviral related proteins. The data extend our understanding of mechanisms underlying Cd accumulation/tolerance and provides possible utilization of elite genetic resources in developing low-grain-Cd barley cultivars.为揭示籽粒镉（Cd）积累量高低各异的两个大麦基因型——浙农8号（Zhenong8）与W6nk2之间的籽粒理化性质与蛋白质组学差异，本研究对二者的籽粒超微结构、氨基酸组成及蛋白质组特征开展了比较分析。结果表明，与浙农8号相比，W6nk2的籽粒总蛋白含量显著更低，其中大麦醇溶蛋白（hordein）的基因型差异最为显著；同时其籽粒氨基酸总量亦更低，尤其是谷氨酸（Glu）、酪氨酸（Tyr）、苯丙氨酸（Phe）与脯氨酸（Pro）的占比显著偏低。扫描电镜与透射电镜观测结果均显示，W6nk2籽粒中A型淀粉粒的粒径显著大于浙农8号。浙农8号的籽粒淀粉颗粒周围富集更多蛋白质沉积体，部分A型淀粉粒表面可见凹陷孔洞。本研究采用双向凝胶电泳（2-DE）结合质谱（mass spectrometry）技术，共鉴定出17个在浙农8号中表达量显著高于W6nk2的籽粒蛋白质，涵盖z型丝氨酸蛋白酶抑制剂（z-type serpin）、serpin-Z7、α-淀粉酶/胰蛋白酶抑制剂CM，以及参与碳水化合物代谢、蛋白质合成与信号转导的相关蛋白。此外，共鉴定出12个在浙农8号中表达量显著低于W6nk2的蛋白质，包括大麦胰蛋白酶抑制剂氯仿/甲醇可溶性蛋白（BTI-CMe2.1、BTI-CMe2.2）、胰蛋白酶抑制剂、脱氢抗坏血酸还原酶（DHAR）、中心粒周蛋白（pericentrin）、动力蛋白重链（dynein heavy chain），以及部分抗病毒相关蛋白。本研究数据加深了我们对籽粒镉积累/耐受分子机制的理解，并为培育低镉籽粒大麦品种提供了优良遗传资源的潜在利用途径。