Green revolution trees: semidwarfism transgenes modify gibberellins, promote root growth, enhance morphological diversity, and reduce competitiveness in hybrid poplar.
Semidwarfism has been used extensively in row crops and horticulture to promote yield, reduce lodging, and improve harvest index, and it might have similar benefits for trees for short-rotation forestry or energy plantations, reclamation, phytoremediation, or other applications. We studied the effects of the dominant semidwarfism transgenes GA Insensitive (GAI) and Repressor of GAI-Like, which affect gibberellin (GA) action, and the GA catabolic gene, GA 2-oxidase, in nursery beds and in 2-year-old high-density stands of hybrid poplar (Populus tremula × Populus alba). Twenty-nine traits were analyzed, including measures of growth, morphology, and physiology. Endogenous GA levels were modified in most transgenic events; GA(20) and GA(8), in particular, had strong inverse associations with tree height. Nearly all measured traits varied significantly among genotypes, and several traits interacted with planting density, including aboveground biomass, root-shoot ratio, root fraction, branch angle, and crown depth. Semidwarfism promoted biomass allocation to roots over shoots and substantially increased rooting efficiency with most genes tested. The increased root proportion and increased leaf chlorophyll levels were associated with changes in leaf carbon isotope discrimination, indicating altered water use efficiency. Semidwarf trees had dramatically reduced growth when in direct competition with wild-type trees, supporting the hypothesis that semidwarfism genes could be effective tools to mitigate the spread of exotic, hybrid, and transgenic plants in wild and feral populations.
Department of Forest Ecosystems and Society, Oregon State University, Corvallis, Oregon 97331, USA.
Ani A
AA
Elias
Victor B
VB
Busov
Kevin R
KR
Kosola
Cathleen
C
Ma
Elizabeth
E
Etherington
Olga
O
Shevchenko
Harish
H
Gandhi
David W
DW
Pearce
Stewart B
SB
Rood
Steven H
SH
Strauss
D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism; D002678:Chimera / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D002734:Chlorophyll / Q000235:genetics / Q000378:metabolism; D003247:Conservation of Natural Resources / Q000379:methods; D016468:Forestry / Q000379:methods; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005838:Genotype; D005875:Gibberellins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018520:Plant Shoots / 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; D014170:Transformation, Genetic; D019076:Transgenes
D002247:Carbon Isotopes; D005875:Gibberellins; D002734:Chlorophyll