Genetic engineering of trees: progress and new horizons

Chang, Shujun; Mahon, Elizabeth L.; MacKay, Heather A.; Rottmann, William H.; Strauss, Steven H.; Pijut, Paula M.; Powell, William A.; Coffey, Vernon; Lu, Haiwei; Mansfield, Shawn D.; Jones, Todd J.

doi:10.1007/s11627-018-9914-1

Cited by 63 publications

(42 citation statements)

References 367 publications

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“…The genus Populus includes about 30 tree species (Eckenwalder, ), many of which are ecologically or commercially important. Owing to their fast growth rate, rapid transition to flowering, amenability to in vitro regeneration and transformation, and established reference genomes (Brunner et al ., ; Tuskan et al ., ; Xue et al ., ; Chang et al ., ), Populus has become an important model system for understanding both tree‐specific traits and perennial angiosperm development (Jansson & Douglas, ; Wullschleger et al ., ).…”

Section: Introductionmentioning

confidence: 99%

RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

Klocko

Brunner

et al. 2019

New Phytologist

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Summary The role of the floral homeotic gene AGAMOUS ( AG ) and its close homologues in development of anemophilous, unisexual catkins has not previously been studied. We transformed two RNA interference ( RNA i) constructs, PTG and its matrix‐attachment‐region flanked version MPG , into the early‐flowering female poplar clone 6K10 ( Populus alba ) to suppress the expression of its two duplicate AG orthologues. By early 2018, six out of 22 flowering PTG events and 11 out of 12 flowering MPG events showed modified floral phenotypes in a field trial in Oregon, USA . Flowers in catkins from modified events had ‘carpel‐inside‐carpel’ phenotypes. Complete disruption of seed production was observed in seven events, and sterile anther‐like organs in 10 events. Events with strong co‐suppression of both the two AG and two SEEDSTICK ( STK ) paralogues lacked both seeds and associated seed hairs. Alterations in all of the modified floral phenotypes were stable over 4 yr of study. Trees from floral‐modified events did not differ significantly ( P < 0.05) from nonmodified transgenic or nontransgenic controls in biomass growth or leaf morphology. AG and STK genes show strong conservation of gene function during poplar catkin development and are promising targets for genetic containment of exotic or genetically engineered trees.

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Section: Introductionmentioning

confidence: 99%

RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

Klocko

Brunner

et al. 2019

New Phytologist

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“…Although transgene-free methods have been developed using the clustered regularly interspersed short palindromic repeat/Cas system to improve perennial plants such as poplar, transgenic technologies are still powerful means to create new traits (Chen et al, 2018). Transgenic technology has been effectively used to produce poplar trees with a variety of useful traits, including herbicide resistance, biotic and abiotic tolerance, improved growth rate, higher nutrient use efficiency, and improved processing and end-use characteristics (Yang et al, 2009;Chang et al, 2018). Although many transgenic field trials have been carried out in the United States, China, and elsewhere, no transgenic trees have been commercially adopted to our knowledge (Li et al, 2016;Klocko et al, 2018).…”

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confidence: 99%

Transgenic Reduction of Cytokinin Levels in Roots Inhibits Root-Sprouting in Populus

Zhai

Strauss

et al. 2019

Plant Physiol.

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Root sprouts-the formation of new shoots from roots-is an important mechanism for local gene flow from poplar (Populus spp). An effective strategy to reduce root sprout formation could therefore help to ensure containment during field research and commercial deployment of poplar when grown as exotic or transgenic forms. We used a flavonoid glycosyltransferase gene promoter from Scutellaria barbata (SbUGT) to drive the expression of AtCKX2, a cytokinin oxidase from Arabidopsis that converts active to inactive cytokinins in roots of poplar. In the greenhouse, SbUGT::AtCKX2 transgenic plants exhibited a similar shoot growth habit, but had enhanced root growth and fewer root sprouts, compared to the wild-type control and transgenic events with low transgene expression in roots. Under field conditions, the transgenic trees also had similar growth habits and stem growth rates that were not statistically different from wild-type trees over 3 years. Removal of trunks generally induced high rates of root sprouting; however, in selected SbUGT::AtCKX2 transgenic poplar events there was an absence or fewer root sprouts compared to wild-type trees, consistent with the greenhouse results. Our study demonstrates that the SbUGT::AtCKX2 gene can effectively inhibit root sprouting of poplar trees under field conditions, and thus may provide a useful tool to address concerns associated with root-sprouting-mediated transgene spread.

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“…In planta and DG overexpression approaches to efficient transformation might not be mutually exclusive; research is warranted to elucidate the potential for DGs to enhance in planta systems. Given the importance of regeneration as a bottleneck to transformation and gene editing of forest trees in research and application ( Chang et al, 2018 ), acceleration of research using both approaches is warranted.…”

Section: Discussionmentioning

confidence: 99%

Opportunities for Innovation in Genetic Transformation of Forest Trees

Nagle

Déjardin²,

Pilate³

et al. 2018

Front. Plant Sci.

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The incorporation of DNA into plant genomes followed by regeneration of non-chimeric stable plants (transformation) remains a major challenge for most plant species. Forest trees are particularly difficult as a result of their biochemistry, aging, desire for clonal fidelity, delayed reproduction, and high diversity. We review two complementary approaches to transformation that appear to hold promise for forest trees.

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Genetic engineering of trees: progress and new horizons

Cited by 63 publications

References 367 publications

RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

Transgenic Reduction of Cytokinin Levels in Roots Inhibits Root-Sprouting in Populus

Opportunities for Innovation in Genetic Transformation of Forest Trees

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