Expression characterization and cross-species complementation uncover the functional conservation of YABBY genes for leaf abaxial polarity and carpel polarity establishment in Saccharum spontaneum.

BACKGROUND: Cell polarity establishment and maintenance is indispensable for plant growth and development. In plants, the YABBY transcription factor family has a distinct role in leaf asymmetric polarity establishment and lateral organ initiation. However, for the important sugar crop Saccharum, little information on YABBY genes is available. RESULTS: In this study, a total of 20 sequences for 7 SsYABBY genes were identified in the sugarcane genome, designated as SsYABBY1-7 based on their chromosome locations, and characterized by phylogenetic analysis. We provided a high-resolution map of SsYABBYs' global expression dynamics during vegetative and reproductive organ morphogenesis and revealed that SsYABBY3/4/5 are predominately expressed at the seedling stage of stem and leaf basal zone; SsYABBY2/5/7 are highly expressed in ovules. Besides, cross-species overexpression and/or complementation verified the conserved function of SsYABBY2 in establishing leaf adaxial-abaxial polarity and ovules development. We found that the SsYABBY2 could successfully rescue the leaves curling, carpel dehiscence, and ovule abortion defects in Arabidopsis crc mutant. CONCLUSIONS: Collectively, our study demonstrates that SsYABBY genes retained a conserved function in establishing and preserving leaf adaxial-abaxial polarity and lateral organ development during evolution.