Lopez Lorena, Camas Alberto, Shivaji Renuka, Ankala Arunkanth, Williams Paul, Luthe Dawn
Department of Biochemistry and Molecular Biology, Mississippi State University, Box 9650, Mississippi State, MS 39762, USA.
Planta. 2007 Jul;226(2):517-27. doi: 10.1007/s00425-007-0501-7. Epub 2007 Mar 10.
When lepidopteran larvae feed on the insect-resistant maize genotype Mp708 there is a rapid accumulation of a defensive cysteine protease, Maize insect resistance 1-cysteine protease (Mir1-CP), at the feeding site. Silver-enhanced immunolocalization visualized with both light and transmission electron microscopy was used to determine the location of Mir1-CP in the maize leaf. The results indicated that Mir1-CP is localized predominantly in the phloem of minor and intermediate veins. After 24 h of larval feeding, Mir1-CP increased in abundance in the vascular parenchyma cells and in the thick-walled sieve element (TSE); it was also found localized to the bundle sheath and mesophyll cells. In situ hybridization of mRNA encoding Mir1-CP indicated that the primary sites of Mir1-CP synthesis in the whorl are the vascular parenchyma and bundle sheath cells. In addition to the phloem, Mir1-CP was also found in the metaxylem of the leaf and root. After 24 h of foliar feeding, the amount of Mir1-CP in the root xylem increased and it appeared to move from xylem parenchyma into the root metaxylem elements. The accumulation of Mir1-CP in maize vascular elements suggests Mir1-CP may move through these tissues to defend against insect herbivores.
当鳞翅目幼虫取食抗虫玉米基因型Mp708时，在取食部位会迅速积累一种防御性半胱氨酸蛋白酶——玉米抗虫1-半胱氨酸蛋白酶（Mir1-CP）。利用银增强免疫定位技术，通过光学显微镜和透射电子显微镜观察，确定了Mir1-CP在玉米叶片中的位置。结果表明，Mir1-CP主要定位于小叶脉和中脉的韧皮部。幼虫取食24小时后，Mir1-CP在维管束薄壁细胞和厚壁筛管分子（TSE）中的丰度增加；在维管束鞘和叶肉细胞中也发现了它的定位。对编码Mir1-CP的mRNA进行原位杂交表明，轮生体中Mir1-CP的主要合成部位是维管束薄壁细胞和维管束鞘细胞。除了韧皮部，在叶片和根的后生木质部中也发现了Mir1-CP。叶面取食24小时后，根木质部中Mir1-CP的含量增加，且似乎从木质部薄壁细胞转移到根后生木质部细胞中。Mir1-CP在玉米维管束细胞中的积累表明，Mir1-CP可能通过这些组织移动以抵御昆虫食草动物。
