Integration of ethylene and jasmonic acid signaling pathways in the expression of maize defense protein Mir1-CP.
In plants, ethylene and jasmonate control the defense responses to multiple stressors, including insect predation. Among the defense proteins known to be regulated by ethylene is maize insect resistance 1-cysteine protease (Mir1-CP). This protein is constitutively expressed in the insect-resistant maize (Zea mays) genotype Mp708; however, its abundance significantly increases during fall armyworm (Spodoptera frugiperda) herbivory. Within 1 h of herbivory by fall armyworm, Mir1-CP accumulates at the feeding site and continues to increase in abundance until 24 h without any increase in its transcript (mir1) levels. To resolve this discrepancy and elucidate the role of ethylene and jasmonate in the signaling of Mir1-CP expression, the effects of phytohormone biosynthesis and perception inhibitors on Mir1-CP expression were tested. Immunoblot analysis of Mir1-CP accumulation and quantitative reverse-transcriptase polymerase chain reaction examination of mir1 levels in these treated plants demonstrate that Mir1-CP accumulation is regulated by both transcript abundance and protein expression levels. The results also suggest that jasmonate functions upstream of ethylene in the Mir1-CP expression pathway, allowing for both low-level constitutive expression and a two-stage defensive response, an immediate response involving Mir1-CP accumulation and a delayed response inducing mir1 transcript expression.
Ankala
A
A
Department of Biochemistry and Molecular Biology, Mississippi State University, Mississipi State, MS 39762, USA.
Luthe
D S
DS
Williams
W P
WP
Wilkinson
J R
JR
D000085:Acetates / Q000494:pharmacology; D003517:Cyclopentanes / Q000378:metabolism* / Q000494:pharmacology; D005030:Ethylenes / Q000378:metabolism* / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D054883:Oxylipins / Q000378:metabolism* / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
D000085:Acetates; D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C011006:jasmonic acid; C072239:methyl jasmonate; C036216:ethylene