|Han, Katherine -|
|Dharmawardhana, P -|
|Arias De Ares, Renee|
|Ma, Cathleen -|
|Busov, Victor -|
|Strauss, Steven -|
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 27, 2010
Publication Date: February 21, 2011
Citation: Han, K.M., Dharmawardhana, P., Arias, R.S., Ma, C., Busov, V., Strauss, S.H. 2011. Gibberellin-associated cisgenes modify growth, stature and wood properties in Populus. Plant Biotechnology Journal. 9(2):162-178. Interpretive Summary: Given the negative perception of the public regarding transgenic plants, cisgenic plants are explored as an avenue to obtain genetic variation without introducing genes from non-related species. The insertion of additional copies of 5 poplar genes involved in plant growth was studied in poplar. The result was high variation in stature, regeneration and stem diameter, which provides breeders with additional germplasm of plant architecture that can be used for multiple applications.
Technical Abstract: We studied the effects on plant growth from insertion of five cisgenes involved in gibberellic acid metabolism or signaling. We cloned intact genomic copies of GA20ox7, GA2ox2, RGL1_1, RGL1_2, and GAI1 genes from the genome sequenced Populus trichocarpa clone Nisqually-1, transformed them into Populus tremula x alba clone (INRA 717-1B4), and characterized growth, morphology, and wood properties in the greenhouse. Three of the cisgenic constructs had significant effects on plant growth rate, plant morphology, or wood properties. The GA20ox7 cisgene increased rate of shoot regeneration in vitro and accelerated early growth, and variation in growth rate was correlated with GA20ox7 gene expression. RGL1_1 reduced growth and caused chlorosis, while RGL1_2 slowed in vitro regeneration and gave rise to plants that grew normally but had longer fiber lengths. There was evidence of co-suppression between the RGL1_2 cissgene and the RGL1_1 endogene, appearing to alleviate the growth-reducing effects expected in the RGL1_2 cisgenic population. Events with the GA2ox2 cisgene had a reduced rate of growth and final stature, and an increased level of chlorosis. GAI1 slowed regeneration rate, and both GAI1 and GA20ox7 imparted an increased variance among events for early diameter and volume index, respectively. This work suggests that insertion of additional copies of native genes involved in growth regulation may provide tools to help modify plant architecture, and to expand the genetic variance in plant architecture available to breeders.