The Juvenile Phase of Maize Sees Upregulation of Stress-Response Genes and Is Extended by Exogenous Jasmonic Acid.
As maize (Zea mays) plants undergo vegetative phase change from juvenile to adult, they both exhibit heteroblasty, an abrupt change in patterns of leaf morphogenesis, and gain the ability to produce flowers. Both processes are under the control of microRNA156 (miR156), whose levels decline at the end of the juvenile phase. Gain of the ability to flower is conferred by the expression of miR156 targets that encode SQUAMOSA PROMOTER-BINDING transcription factors, which, when derepressed in the adult phase, induce the expression of MADS box transcription factors that promote maturation and flowering. How gene expression, including targets of those microRNAs, differs between the two phases remains an open question. Here, we compare transcript levels in primordia that will develop into juvenile or adult leaves to identify genes that define these two developmental states and may influence vegetative phase change. In comparisons among successive leaves at the same developmental stage, plastochron 6, three-fourths of approximately 1,100 differentially expressed genes were more highly expressed in primordia of juvenile leaves. This juvenile set was enriched in photosynthetic genes, particularly those associated with cyclic electron flow at photosystem I, and in genes involved in oxidative stress and retrograde redox signaling. Pathogen- and herbivory-responsive pathways including salicylic acid and jasmonic acid also were up-regulated in juvenile primordia; indeed, exogenous application of jasmonic acid delayed both the appearance of adult traits and the decline in the expression of miR156-encoding loci in maize seedlings. We hypothesize that the stresses associated with germination promote juvenile patterns of differentiation in maize.
Department of Biology, University of Iowa, Iowa City, Iowa 52242.
Benjamin
0000-0001-9499-0209
B
Beydler
Department of Biology, University of Iowa, Iowa City, Iowa 52242.
Krista
K
Osadchuk
Department of Biology, University of Iowa, Iowa City, Iowa 52242.
Chi-Lien
0000-0003-3188-047X
CL
Cheng
Department of Biology, University of Iowa, Iowa City, Iowa 52242.
J Robert
JR
Manak
Department of Biology, University of Iowa, Iowa City, Iowa 52242 erin-irish@uiowa.edu.
Erin E
0000-0003-4244-7938
EE
Irish
D016000:Cluster Analysis; D003517:Cyclopentanes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D063990:Gene Ontology; D017343:Genes, Plant; D059372:Nucleotide Motifs / Q000235:genetics; D054883:Oxylipins / Q000494:pharmacology*; D052585:Phloem / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*
D003517:Cyclopentanes; D054883:Oxylipins; D012333:RNA, Messenger; C011006:jasmonic acid