State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.
Plant Cell Environ. 2012 Apr;35(4):770-89. doi: 10.1111/j.1365-3040.2011.02450.x. Epub 2011 Nov 15.
Type 4 metallothionein (MT) genes are recognized for their specific expression in higher plant seeds, but their functions are still unclear. In this study, the functions of two Arabidopsis metallothionein genes, AtMT4a and AtMT4b, are investigated in seed development, germination and early seedling growth. Transcriptional analysis showed that these two genes are specifically expressed in late embryos. Subcellular localization displayed that both AtMT4a and AtMT4b are widespread distributed in cytoplasm, nucleus and membrane. Co-silencing RNAi of AtMT4a and AtMT4b reduced seed weight and influenced the early seedling growth after germination, whereas overexpression of these two genes caused the opposite results. Detailed analysis showed clearly the correlation of AtMT4a and AtMT4b to the accumulation of some important metal ions in late embryos, especially to Zn ion storing in seeds, which then serves as part of early Zn ion resources for post-germinated seedling growth. Furthermore, phytohormone abscisic acid (ABA) and gibberellic acid (GA) may play roles in regulating the expression and function of AtMT4a and AtMT4b during seed development; and this may influence Zn accumulation in seeds and Zn ion nutrient supplementation in the early seedling growth after germination.
4 型金属硫蛋白（MT）基因因其在高等植物种子中的特异性表达而被认可，但它们的功能仍不清楚。在这项研究中，研究了拟南芥金属硫蛋白基因 AtMT4a 和 AtMT4b 在种子发育、萌发和早期幼苗生长中的功能。转录分析表明，这两个基因在晚期胚胎中特异性表达。亚细胞定位显示，AtMT4a 和 AtMT4b 均广泛分布于细胞质、细胞核和膜中。AtMT4a 和 AtMT4b 的共沉默 RNAi 降低了种子重量，并影响了萌发后早期幼苗的生长，而这些基因的过表达则产生了相反的结果。详细分析清楚地表明，AtMT4a 和 AtMT4b 与晚期胚胎中一些重要金属离子的积累有关，特别是与种子中 Zn 离子的储存有关，这些 Zn 离子随后成为萌发后幼苗生长中早期 Zn 离子资源的一部分。此外，植物激素脱落酸（ABA）和赤霉素（GA）可能在种子发育过程中调节 AtMT4a 和 AtMT4b 的表达和功能；这可能影响种子中 Zn 的积累和萌发后早期幼苗生长中 Zn 离子的营养补充。
