Minisymposium 10: Cell Division

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Abs # M1001: The ATK5 and ATK1 kinesins that are critical for meiotic spindle morphogenesis and gametophyte development in Arabidopsis

Presenter:	Quan, Li       Contact Presenter
Authors	Quan, Li  (A) (B)  Xiao, Rong  (A) (C)  Li, Wuxing  (A) (C)  Oh, Sung-Aeong  (D)   Ambrose, Christian J. (B) (E)  Cyr, Richard J. (A) (C)  Twell, David  (D)   Ma, Hong  (A) (B)
Affiliations:	(A): Department of Biology, the Pennsylvania State University, University Park, PA 16802, USA (B): The Huck Institutes of the Life Sciences, the Pennsylvania State University, University Park, PA 16802, USA (C): The Intercollege Graduate Program in Plant Physiology, the Pennsylvania State University, University Park, PA 16802, USA (D): Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom (E): Integrative Biosciences Graduate Degree Program, the Pennsylvania State University, University Park, PA 16802, USA

Kinesins are motor proteins that bind to and move along microtubules by using the energy released from ATP hydrolysis. Kinesins in various organisms have been reported to be important for the assembly and maintenance of the spindle, which is critical for proper chromosome segregation during mitosis and meiosis. Here, we report that one Arabidopsis kinesin gene, ATK5, which shares extremely high levels of sequence similarity with another kinesin gene ATK1 across the entire coding region, is functionally redundant to each other. Among the self-progeny of ATK1/atk1 ATK5/atk5 double heterozygous plants, plants of three genotypes, ATK1/atk1 atk5/atk5, atk1/atk1 ATK5/atk5, and atk1/atk1 atk5/atk5, were not recovered. Double reciprocal experiment indicated that the double heterozygous plant could not transmit the atk1 and atk5 mutant alleles simultaneously through either male or female gametes, suggesting that at least one copy of the ATK1 and ATK5 genes is required for gametophyte development and/or function. The absence of progeny plants of these three genotypes could be partially rescued by the introduction of a wild-type copy of ATK5 driven by CaMV 35S promoter into the ATK1/atk1 ATK5/atk5 plants. Although fertility of the double heterozygous plant was still quite high, approximately 50% of pollen and ovules in the ATK1/atk1 ATK5/atk5 plant were aborted. Cytological experiments revealed that in the double heterozygous plant a large number of male meiotic cells had defective spindle structures. In addition, the metaphase I stage spindle had a multi-axial composition, resulting in abnormal chromosomal alignment and segregation which was proposed to be the cause for various numbers of microspores in tetrad cells (up to 10 microspores from each meiotic cell). In addition, female reproductive organs in the double heterozygous plant also exhibited defects in ovule development. These results indicate that both ATK5 and ATK1 have overlapping function required for spindle morphogenesis during male meiosis in Arabidopsis, possibly with dosage-dependent manners. Therefore, ATK5 and ATK1 genes together play important roles in controlling plant reproductive development.