The autophosphorylated Ser686, Thr688, and Ser689 residues in the intracellular juxtamembrane domain of XA21 are implicated in stability control of rice receptor-like kinase.
The rice gene Xa21 confers resistance against Xanthomonas oryzae pv. oryzae (Xoo). Xa21 encodes a receptor-like kinase (XA21). We demonstrate that XA21 autophosphorylates residues Ser686, Thr688 and Ser689 in vitro. Substitution of these residues with alanines did not affect the autophosphorylation function of this kinase, but specifically destabilized the resistance protein in vitro and in vivo. Plants carrying these same substitutions in XA21 were compromised in their resistance to the normally avirulent Xoo Philippine race 6. Additionally, we show that wild-type XA21 and the kinase-dead mutant with the invariable Lys736 residue mutated to glutamic acid were also proteolytically degraded in protein extracts. Finally, we show a correlation between the in vitro degradation and in vivo instability of the proteins. We propose that autophosphorylation of Ser686, Thr688 and Ser689 functions to stabilize XA21 against the developmentally controlled proteolytic activity.
Xu
Wei-Hui
WH
Department of Plant Pathology, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA.
Wang
Yong-Sheng
YS
Liu
Guo-Zhen
GZ
Chen
Xiuhua
X
Tinjuangjun
Porntip
P
Pi
Li-Ya
LY
Song
Wen-Yuan
WY
D019943:Amino Acid Substitution; D042541:Intracellular Space; D008861:Microsomes / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D012275:Oryza / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology; D010766:Phosphorylation; D010940:Plant Proteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*; D014974:Xanthomonas
D050505:Mutant Proteins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C097148:Xa21 protein, Oryza sativa; D013912:Threonine; D012694:Serine; D017346:Protein Serine-Threonine Kinases