Identification of evolutionarily conserved amino acid residues in homeodomain of KNOX proteins for intercellular trafficking

Abstract

Maize KNOTTED (KN1) homeodomain (HD) protein is a well-known mobile transcription factor crucial for stem cell maintenance. Recent studies have revealed that the trihelical HD of KNOTTED1-like homeobox (KNOX) proteins is necessary and sufficient for selective cell-to-cell trafficking. Also, the efficient trafficking ability for HD is likely to be acquired during the evolution of early nonvascular land plants. Here, using the point-mutated HD of KN1 and SHOOT MERISTEMLESS (STM) in the trichome rescue system, together with molecular structure modeling, we have found the evolutionarily conserved amino acid residues, such as arginine in helix α1 and leucine in helix α3, which are essential for intercellular trafficking. Our studies provided important clues for the 3-dimensional protein structure required for cell-to-cell movement of non-cell-autonomous transcription factors.

Keywords: :

• homeodomain
• intercellular protein trafficking
• non-cell-autonomous
• plasmodesmata
• transcription factor

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were declared by authors.

Acknowledgments

We thank Y Lee (Gyeongsang National University) for rmsd calculation. This work was supported by Basic Science Research Program (NRF-2013R1A1A2007230) through the National Research Foundation of Korea funded by the Ministry of Education, the Next-Generation BioGreen 21 Program (SSAC, grant PJ009495), Rural Development Administration, Republic of Korea, and the National Science Foundation (NSF – IOS-1027003).