Gibberellins regulate lateral root formation in Populus through interactions with auxin and other hormones.
The role of gibberellins (GAs) in regulation of lateral root development is poorly understood. We show that GA-deficient (35S:PcGA2ox1) and GA-insensitive (35S:rgl1) transgenic Populus exhibited increased lateral root proliferation and elongation under in vitro and greenhouse conditions, and these effects were reversed by exogenous GA treatment. In addition, RNA interference suppression of two poplar GA 2-oxidases predominantly expressed in roots also decreased lateral root formation. GAs negatively affected lateral root formation by inhibiting lateral root primordium initiation. A whole-genome microarray analysis of root development in GA-modified transgenic plants revealed 2069 genes with significantly altered expression. The expression of 1178 genes, including genes that promote cell proliferation, growth, and cell wall loosening, corresponded to the phenotypic severity of the root traits when transgenic events with differential phenotypic expression were compared. The array data and direct hormone measurements suggested crosstalk of GA signaling with other hormone pathways, including auxin and abscisic acid. Transgenic modification of a differentially expressed gene encoding an auxin efflux carrier suggests that GA modulation of lateral root development is at least partly imparted by polar auxin transport modification. These results suggest a mechanism for GA-regulated modulation of lateral root proliferation associated with regulation of plant allometry during the stress response.
Gou
Jiqing
J
School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, Michigan 49931-1295, USA.
Strauss
Steven H
SH
Tsai
Chung Jui
CJ
Fang
Kai
K
Chen
Yiru
Y
Jiang
Xiangning
X
Busov
Victor B
VB
D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D032107:Populus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction
D005875:Gibberellins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D018749:RNA, Plant