Mir1-CP, a novel defense cysteine protease accumulates in maize vascular tissues in response to herbivory.
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.
Lopez
Lorena
L
Department of Biochemistry and Molecular Biology, Mississippi State University, Box 9650, Mississippi State, MS 39762, USA. lml113@ra.msstate.edu
Camas
Alberto
A
Shivaji
Renuka
R
Ankala
Arunkanth
A
Williams
Paul
P
Luthe
Dawn
D
D000818:Animals; D002473:Cell Wall / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000032:analysis / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D007915:Lepidoptera / Q000502:physiology; D052585:Phloem / Q000166:cytology / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D018087:Plastids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D052584:Xylem / Q000166:cytology / Q000378:metabolism; D003313:Zea mays / Q000166:cytology / Q000378:metabolism* / Q000469:parasitology
D010940:Plant Proteins; D012333:RNA, Messenger; D003546:Cysteine Endopeptidases