Poster: Reproductive Development

Abs # 483: Expression of CP4 EPSPS in microspores and tapetum Is critical for the male reproductive success in glyphosate-resistant cotton (Gossypium hirsutum)

Presenter:	Chen, Sophia Y, sophia.y.chen@monsanto.com
Authors	Chen, Sophia Y (A)   Hubmeier, Christopher S (A)   Tran, Minhtien  (A)   Martens, Amy B (A)   Cerny, Eric  (A)   CaJacob, Claire A (A)
Affiliations:	(A): Monsnato Company

Plants expressing sufficient amount of Agrobacterium sp. strain CP4 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) are known to possess resistance to glyphosate, a potent herbicide that inhibits the activity of the endogenous EPSPS. The transgenic cotton line, RR1445, was generated using the figwort mosaic virus (FMV35S) promoter to drive the expression of the CP4 EPSPS gene and has excellent vegetative tolerance to glyphosate. However, with high glyphosate application rates at late developmental stages (5-leaf and beyond)*, RR1445 shows male sterility. Another transgenic cotton line, RR60, which was generated using the FMV35S promoter and a plant promoter for the expression of CP4 EPSPS, has excellent vegetative and reproductive tolerance to late-stage applications of glyphosate. Histochemical analyses were conducted to dissect the male reproductive development of these two cotton lines in response to glyphosate applications at the cellular level, as well as the correlation between glyphosate injury and the expression of CP4 EPSPS in male reproductive tissues. The expression of CP4 EPSPS in RR60 was found to be strong in all male reproductive cell types. Conversely, CP4 EPSPS in RR1445 was shown to be almost non-detectable in pollen mother cells, male gametophytes and tapetum, three crucial male reproductive cell types. Our results indicate that the FMV35S promoter, although expressing strongly in most vegetative tissues in plants, has extremely low activity in these cell types. Other viral promoters may share this expression pattern in plants as well. *late-stage applications: applications that are inconsistent with the Roundup® labels.