Poster: Reproductive Development

Abs # 478: DROOPING LEAF regulates carpel identity and promotes midrib formation in rice (Oryza sativa).

Presenter:	Yamaguchi, Takahiro , aa07013@mail.ecc.u-tokyo.ac.jp
Authors	Yamaguchi, Takahiro  (A)   An, Gynheung  (B)   Miyao, Akio  (C)   Hirochika, Hirohiko  (C)   Hirano, Hiro-Yuki  (A)
Affiliations:	(A): Graduate School of Agricultural and Life Sciences, University of Tokyo (B): Pohang University of Science and Technology (C): National Institute of Agrobiological Resources

In monocots, the mechanism of floral organ specification is not fully understood. We have isolated DOOPING LEAF (DL), of which loss-of-function causes the transformation of carpels into stamens and indeterminate floral meristem. DL encodes a transcription factor of YABBY family protein, which is closely related to CRABS CLAW (CRC) in Arabidopsis, and is expressed specifically in carpel primordium. Expression analyses of DL and MADS-box genes in the floral homeotic mutants such as dl, superwoman1 (spw1) and plants constitutively expressing SPW1 indicate that DL is essential for carpel specification and interacts antagonistically with the B-function genes. It is also suggested that DL functions independent or downstream of the C-function genes and may be negatively regulated by putative A-function genes. These studies indicate that genetic relationships of DL/CRC with the ABC-function genes are fundamentally conserved between rice and Arabidopsis, but it is supposed that DL plays more essential roles in carpel specification in rice. To reveal the roles of the C-function genes in reproductive organ specification of rice and the genetic relationships with DL, approaches to isolate knock-out lines of the C-function genes are in progress. Finally, loss-of-function of DL shows midribless phenotype. DL is expressed in the central region of developing leaves and over-expression of DL under constitutive promoter expanded the midrib domain into lateral domains. These results indicate that DL promotes midrib formation. Together with the function and expression in flower development, DL may not be involved in abaxial specification such as YABBY genes in Arabidopsis.