A multilayered regulatory mechanism for the autoinhibition and activation of a plant CC-NB-LRR resistance protein with an extra N-terminal domain
X. TAO (1), X. Chen (2), M. Zhu (2), L. Jiang (2), W. Zhao (2), J. Li (2), J. Wu (2), C. Li (2), B. Bai (2), G. Lu (2), H. Chen (2) (1) Nanjing Agricultural University, China; (2) Nanjing Agricultural University, China

Compared with classical coil-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) resistance proteins, tomato Sw-5b has evolved an extra N-terminal domain (NTD). However, it is not known why this CC-NB-LRR protein evolved an extra NTD. In this study, we used the tomato Sw-5b as our model to address the regulatory role of NTD on CC/NB-LRR. We found that the Sw-5b NB-LRR segment has the basic function of a plant resistance protein for autoinhibition and for viral elicitor-dependent activation. Structural modeling and functional experiments showed that LRR sequestered the central NB-ARC in an autoinhibited state. The CC and NTD domains independently and additively enhanced the autoinhibition of NB-LRR in the absence of elicitor. Surprisingly, unlike the CC domain of classical CC-NB-LRR proteins, Sw-5b CC dampened NB-LRR activation even in the presence of elicitor. Importantly, the extra N-terminal domain became a positive regulator in the presence of elicitor and fully activated the resistance protein, probably by relieving the inhibitory effects of CC. This regulation is essential for virus resistance. Based on these findings, we propose that, to resolve the negative regulation of CC on NB-LRR, Sw-5b evolved an extra domain at the N-terminus to coordinate with CC, and consequently, Sw-5b developed a multilayered autoinhibition/activation to regulate its activity.

Abstract Number: P17-623
Session Type: Poster