Genome-wide identification of PTI1 family in Setaria italica and salinity-responsive functional analysis of SiPTI1\u20135

Yongguan Huangfu,Qingguo Wang,Fatemeh Mastouri,Ying Li,Min Liu,Zhen Li,Wei Liu,Jiaowen Pan,Stephen Yang,Shaojun Dai

doi:10.1186/s12870-021-03077-4

Abstract

BackgroundPTI1 (Pto-interacting 1) protein kinase belongs to the receptor-like cytoplasmic kinase (RLCK) group of receptor-like protein kinases (RLK), but lack extracellular and transmembrane domains. PTI1 was first identified in tomato (Solanum lycopersicum) and named SlPTI1, which has been reported to interact with bacterial effector Pto, a serine/threonine protein kinase involved in plant resistance to bacterial disease. Briefly, the host PTI1 specifically recognizes and interacts with the bacterial effector AvrPto, which triggers hypersensitive cell death to inhibit the pathogen growth in the local infection site. Previous studies have demonstrated that PTI1 is associated with oxidative stress and hypersensitivity.ResultsWe identified 12 putative PTI1 genes from the genome of foxtail millet (Setaria italica) in this study. Gene replication analysis indicated that both segmental replication events played an important role in the expansion of PTI1 gene family in foxtail millet. The PTI1 family members of model plants, i.e. S. italica, Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa), maize (Zea mays), S. lycopersicum, and soybean (Glycine max), were classified into six major categories according to the phylogenetic analysis, among which the PTI1 family members in foxtail millet showed higher degree of homology with those of rice and maize. The analysis of a complete set of SiPTI1 genes/proteins including classification, chromosomal location, orthologous relationships and duplication. The tissue expression characteristics revealed that SiPTI1 genes are mainly expressed in stems and leaves. Experimental qRT-PCR results demonstrated that 12 SiPTI1 genes were induced by multiple stresses. Subcellular localization visualized that all of foxtail millet SiPTI1s were localized to the plasma membrane. Additionally, heterologous expression of SiPTI1–5 in yeast and E. coli enhanced their tolerance to salt stress.ConclusionsOur results contribute to a more comprehensive understanding of the roles of PTI1 protein kinases and will be useful in prioritizing particular PTI1 for future functional validation studies in foxtail millet.

Highlights

Pto-interacting 1 genes (PTI1s) (Pto-interacting 1) protein kinase belongs to the receptor-like cytoplasmic kinase (RLCK) group of receptor-like protein kinases (RLK), but lack extracellular and transmembrane domains
In view of the fact that PTI1 proteins participate in a variety of stress defense responses and no PTI1 was previously identified in foxtail millet, we decided to further analyze the PTI1 gene family in foxtail millet to identify those responsive to salt stress and explore their application in crop improvement
A total of 12 putative PTI1 genes were identified in foxtail millet via genome-wide analysis (Table 1, Additional file 1)

Summary

Introduction

PTI1 (Pto-interacting 1) protein kinase belongs to the receptor-like cytoplasmic kinase (RLCK) group of receptor-like protein kinases (RLK), but lack extracellular and transmembrane domains. PTI1 was first identified in tomato (Solanum lycopersicum) and named SlPTI1, which has been reported to interact with bacterial effector Pto, a serine/threonine protein kinase involved in plant resistance to bacterial disease. The host PTI1 recognizes and interacts with the bacterial effector AvrPto, which triggers hypersensitive cell death to inhibit the pathogen growth in the local infection site. It was first identified in tomato and was demonstrated to recognize and interact with the AvrPto effector protein injected into the plant cells by the pathogenic bacteria, thereby triggering the downstream defense response [3]. OXI1-PTI1 is involved in the activation of the MAPK signaling pathway, which in turn responds to oxidative and biotic stresses [8, 16]. Overexpression of OsPTI1 increases rice resistance to fungal invasion [14]

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Results

Conclusion