Mutation of the rice XA21 predicted nuclear localization sequence does not affect resistance to Xanthomonas oryzae pv. oryzae

Tong Wei; Tsung-Chi Chen; Yuen Ting Ho; Pamela C Ronald

doi:10.7717/peerj.2507

Mutation of the rice XA21 predicted nuclear localization sequence does not affect resistance to Xanthomonas oryzae pv. oryzae

PeerJ. 2016 Oct 5:4:e2507. doi: 10.7717/peerj.2507. eCollection 2016.

Authors

Tong Wei^#^{1

2

3}, Tsung-Chi Chen^#¹, Yuen Ting Ho¹, Pamela C Ronald^{1

2

3}

Affiliations

¹ Department of Plant Pathology and the Genome Center, University of California, Davis, CA, United States.
² Feedstocks Division, Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
³ Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.

^# Contributed equally.

Abstract

Background: The rice receptor kinase XA21 confers robust resistance to the bacterial pathogen Xanthomonas oryzaepv. oryzae(Xoo). We previously reported that XA21 is cleaved in transgenic plants overexpressing XA21 with a GFP tag (Ubi-XA21-GFP) and that the released C-terminal domain is localized to the nucleus. XA21 carries a predicted nuclear localization sequence (NLS) that directs the C-terminal domain to the nucleus in transient assays, whereas alanine substitutions in the NLS disrupt the nuclear localization.

Methods: To determine if the predicted NLS is required for XA21-mediated immunity in planta, we generated transgenic plants overexpressing an XA21 variant carrying the NLS with the same alanine substitutions (Ubi-XA21nls-GFP).

Results: Ubi-XA21nls-GFP plants displayed slightly longer lesion lengths, higher Xoobacterial populations after inoculation and lower levels of reactive oxygen species production compared with the Ubi-XA21-GFP control plants. However, the Ubi-XA21nls-GFP plants express lower levels of protein than that observed in Ubi-XA21-GFP.

Discussion: These results demonstrate that the predicted NLS is not required for XA21-mediated immunity.

Keywords: Bacterial blight disease; Nuclear localization; XA21-mediated immunity; Xanthomonas oryzae pv. oryzae.

Grants and funding

The work was supported by NIH GM59962 to Pamela C. Ronald. The work conducted by the Joint BioEnergy Institute was supported by the Office of Science, Office of Biological and Environmental Research, of the US Department of Energy under Contract No. DE-AC02-05CH11231. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.