Comparison of the impact of viral and plant-derived promoters regulating selectable marker gene on maize transformation and transgene expression.
The choice of promoter regulating the selectable marker gene impacts transformation efficiency, copy number and the expression of selectable marker and flanking genes in maize. Viral or plant-derived constitutive promoters are often used to regulate selectable marker genes. We compared two viral promoters, cauliflower mosaic virus (CaMV 35T) and sugarcane bacilliform virus (SCBV) with two plant promoters, rice actin1 (OsAct1) and maize ubiquitin 1 (ZmUbi1) to drive aryloxyalkanoate dioxygenase (aad-1) selectable marker gene in maize inbred line B104. ZmUbi1- and OsAct1-containing constructs demonstrated higher transformation frequencies (43.8 and 41.4%, respectively) than the two viral promoter constructs, CaMV 35T (25%) and SCBV (8%). Interestingly, a higher percentage of single copy events were recovered for SCBV (82.1%) and CaMV 35T (59.3%) promoter constructs, compared to the two plant-derived promoters, OsAct1 (40.0%), and ZmUbi1 (27.6%). Analysis of protein expression suggested that the viral promoter CaMV 35T expressed significantly higher AAD-1 protein (174.6 ng/cm2) than the OsAct1 promoter (12.6 ng/cm2) in T0leaf tissue. When measured in T2callus tissue, the two viral promoters both had higher expression and more variability than the two plant-derived promoters. A potential explanation for why viral promoters produce lower transformation efficiencies but higher percentages of low copy number events is discussed. In addition, viral promoters regulating aad-1 were found to influence the expression of upstream flanking genes in both T0leaf and T2callus tissue.
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Jeffrey
J
Beringer
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Wei
W
Chen
Covance, Inc., 8211 SciCor Drive, Indianapolis, IN, 46214, USA.
Russell
R
Garton
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Nagesh
N
Sardesai
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Po-Hao
PH
Wang
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Ning
N
Zhou
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA.
Manju
M
Gupta
Dow AgroSciences, LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA. hwu2@dow.com.
Huixia
http://orcid.org/0000-0002-1838-3383
H
Wu
D017796:Caulimovirus / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014170:Transformation, Genetic / Q000235:genetics*; D019076:Transgenes / Q000235:genetics*; D003313:Zea mays / Q000235:genetics*
Aad-1 and yfp genes; Copy number; Gene expression; Maize; Promoter choice; Transformation efficiency