Plants on constant alert: elevated levels of jasmonic acid and jasmonate-induced transcripts in caterpillar-resistant maize.
This study was conducted to determine if constitutive levels of jasmonic acid (JA) and other octadecanoid compounds were elevated prior to herbivory in a maize genotype with documented resistance to fall armyworm (Spodoptera frugiperda) and other lepidopteran pests. The resistant inbred Mp708 had approximately 3-fold higher levels of jasmonic acid (JA) prior to herbivore feeding than the susceptible inbred Tx601. Constitutive levels of cis-12-oxo-phytodienoic acid (OPDA) also were higher in Mp708 than Tx601. In addition, the constitutive expression of JA-inducible genes, including those in the JA biosynthetic pathway, was higher in Mp708 than Tx601. In response to herbivory, Mp708 generated comparatively higher levels of hydrogen peroxide, and had a greater abundance of NADPH oxidase transcripts before and after caterpillar feeding. Before herbivore feeding, low levels of transcripts encoding the maize insect resistance cysteine protease (Mir1-CP) and the Mir1-CP protein were detected consistently. Thus, Mp708 appears to have a portion of its defense pathway primed, which results in constitutive defenses and the ability to mount a stronger defense when caterpillars attack. Although the molecular mechanisms that regulate the constitutive accumulation of JA in Mp708 are unknown, it might account for its enhanced resistance to lepidopteran pests. This genotype could be valuable in studying the signaling pathways that maize uses to response to insect herbivores.
Department of Biochemistry and Molecular Biology, Mississippi State University, Mississippi State, MS 39762, USA.
Renuka
R
Shivaji
Alberto
A
Camas
Arunkanth
A
Ankala
Jurgen
J
Engelberth
James H
JH
Tumlinson
W Paul
WP
Williams
Jeff R
JR
Wilkinson
Dawn Sywassink
DS
Luthe
D000818:Animals; D001947:Breeding; D003517:Cyclopentanes / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D007915:Lepidoptera / Q000502:physiology*; D019255:NADPH Oxidases / Q000235:genetics; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics; D054883:Oxylipins / Q000378:metabolism*; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D003313:Zea mays / Q000166:cytology / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; C025999:12-oxophytodienoic acid; C011006:jasmonic acid; D006861:Hydrogen Peroxide; D044925:Oxidoreductases Acting on CH-CH Group Donors; C106360:12-oxophytodienoate reductase; D019255:NADPH Oxidases