Female gametophytes and flowering plant reproduction: Green eggs and no SAM

PANOLI, ANEESH , SONG, XIAOY , CONRAD, LIZA , ANDERSON, SARAH , PAGNUSSAT, GABRIELA , ALANDETE-SAEZ, MONICA , CHEN, GAIPING , RUSSELL, SCOTT , SUNDARESAN, VENKATESAN

Portland

Conferencia; 54 th Annual Maize Genetics Conference; 2012

Female gametophytes and flowering plant reproduction: Green eggs and no SAM Panoli, Aneesh 1 , Song, Xiaoya 1 , Conrad, Liza 1 , Anderson, Sarah 1 , Pagnussat, Gabriela 1 , Alandete-Saez, Monica 1 , Chen, Gaiping 2 , Russell, Scott 2 , Sundaresan, Venkatesan 1 1 Department of Plant Biology and Plant Sciences, University of California-Davis, CA 95616 2 Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019 The reproduction of flowering plants involves the formation of gametic cells by the haploid male (pollen) and female (embryo sac) gametophytes, In most angiosperms, the female gametophyte contains just 7 cells including two gametes, the egg cell and the central cell, which give rise to the embryo and endosperm respectively. The embryo sac first develops as a syncytium of 8 nuclei, which are partitioned into 7 cells upon cellularization. Cell fates in the embryo sac are determined immediately depending upon nuclear positioning; there are no undifferentiated cells that typify sporophytic development, e.g., as in the shoot apical meristem. Signaling by the hormone auxin plays an important role in position based cell identity in the Arabidopsis embryo sac, through an asymmetric auxin distribution generated during female gametophyte development. The highest auxin levels are at the distal pole corresponding to the egg cell and the synergid cells, and these cell fates can be altered by manipulation of auxin signaling. The auxin distribution appears to be correlated with localized biosynthesis, rather than auxin efflux, which plays a more important role in sporophytic patterning. An asymmetric cytokinin distribution might also be acting to promote cell fates within the embryo sac. We have also begun to investigate the reprogramming of the differentiated egg cell to a totipotent zygote after fertilization. Preliminary results using rice suggests that the maternal to zygotic transition in plants is initiated as early as the first cell cycle of the zygote, much earlier than has been observed in animals. Funding acknowledgement: National Science Foundation (NSF) and National Institute of Food & Agriculture, USDA 23