Poster: Cytoskeleton structure & dynamics

Abs # 684: The effects of ~{&A~}-NAA on the growth of Chara, and the Cytoskeletal changes during maturation of sexual organs in Chara

Presenter:	Jin, Qiaojun , jqiaojun@yahoo.com
Authors	Jin, Qiaojun  (A)   Hasenstein, Karl  (A)
Affiliations:	(A): University of Louisiana, at Lafayette

Auxin is an important plant growth regulator. However, the understanding of the effects of auxin on the growth of green algae Chara is far from complete. We used α-NAA as a functional analog of auxin and analyzed its effects on Chara. The elongation of thalli were significantly induced in the first 30 days, but were inhibited thereafter by 10-5 M α-NAA. 10-5 M α-NAA also depolymerized the microtubules in the whorl cells, as well as the microtubules of the tip cell of the lateral branch after 8 hrs of incubation. α-NAA may also affect the endogenous auxin level in Chara, which will be measured. We also plan to investigate the effect of α-NAA on the sexual organs of Chara. The developmental cytoskeletal changes during maturation of antheridia and oogonia in Chara have been studied by confocal laser scanning microscopy. The antheridial filament undergoes synchronized cell division during which cortical MTs, metaphase spindle, telophase spindle, and phragmoplasts were observed. The MT revealed striking and unusual patterns. At the end of telophase, the nucleus forms a spiral of about 2.5 turns. Cells within the oogonia were organized into an eight-cell format, similar to the embryo sac in high plants. These observations underscore the close relationship between chara and higher plants.