Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway.
The genome of the Mastreviruses encodes a replication-associated protein (RepA) that interacts with members of the plant retinoblastoma-related protein family, which are putative cell cycle regulators. Expression of ZmRb1, a maize retinoblastoma-related gene, and RepA inhibited and stimulated, respectively, cell division in tobacco cell cultures. The effect of RepA was mitigated by over-expression of ZmRb1. RepA increased transformation frequency and callus growth rate of high type II maize germplasm. RepA-containing transgenic maize calli remained embryogenic, were readily regenerable, and produced fertile plants that transmitted transgene expression in a Mendelian fashion. In high type II, transformation frequency increased with the strength of the promoter driving RepA expression. When a construct in which RepA was expressed behind its native LIR promoter was used, primary transformation frequencies did not improve for two elite Pioneer maize inbreds. However, when LIR:RepA-containing transgenic embryos were used in subsequent rounds of transformation, frequencies were higher in the RepA+ embryos. These data demonstrate that RepA can stimulate cell division and callus growth in culture, and improve maize transformation.
Gordon-Kamm
William
W
Pioneer Hi-Bred, International, Inc., Johnston, IA 50131, USA. william.gordon-kamm@pioneer.com
Dilkes
Brian P
BP
Lowe
Keith
K
Hoerster
George
G
Sun
Xifan
X
Ross
Margit
M
Church
Laura
L
Bunde
Chris
C
Farrell
Jeff
J
Hill
Patrea
P
Maddock
Sheila
S
Snyder
Jane
J
Sykes
Louisa
L
Li
Zhongsen
Z
Woo
Young-min
YM
Bidney
Dennis
D
Larkins
Brian A
BA
D002453:Cell Cycle; D002455:Cell Division; D004265:DNA Helicases; D004268:DNA-Binding Proteins; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011506:Proteins / Q000502:physiology; D016160:Retinoblastoma Protein / Q000378:metabolism*; D015534:Trans-Activators; D003313:Zea mays / Q000166:cytology* / Q000378:metabolism
D004268:DNA-Binding Proteins; D011506:Proteins; D016160:Retinoblastoma Protein; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases