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Abstract Detail



Developmental and Structural Section

Pesacreta, Thomas [1].

F-actin and actin2 transcript distribution and protophloem anatomy in angiosperm and gymnosperm root primary tissues. Pesacreta, T.C., Purpera, M., and Kumar, M. Microscopy Center and Biology Dept., University of Louisiana, Lafayette 70504.

The fossil record implies an independent origin for roots in lycopods, a line that did not lead to seed plants. Within the remaining land plant lineages the steps in the evolution of roots are unknown. A comparison of actin RNA levels in the distal portions of angiosperm and gymnosperm roots reveals distinctly different patterns. In Zea mays, the actin2 transcript level is lowest in the 0 to 3 mm region and higher in the 3 to 6 mm region. In Pinus pinea the reverse is true for a similar transcript. The distribution of F-actin in roots was analyzed with fluorescent phalloidin. In Zea and Vigna F-actin is concentrated in the vascular cylinder, relative to the cortex. In isolated cases is it possible to detect a concentration of F-actin in a specific cell type within the vascular cylinder - pericycle cells that abut the first mature protophloem sieve elements. In gymnosperms the protophloem lacks sieve elements, instead having many (depending on root diameter) highly vacuolated parenchyma cells. These parenchymatous protophloem cells differentiate near the apex and are distinguishable from the surrounding cell types by their extensive F-actin arrays. The function of these cells has not been established but a role in translocation is possible. These differences between angiosperms and gymnosperms show that the evolution of roots in these two groups followed two separate paths.

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1 - University of Louisiana, 300 East Saint Mary St., PO Box 42451, Lafayette, LA, 70504, USA

Keywords:
gymnosperms
phloem.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PDS010
Abstract ID:308
Candidate for Awards:None


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