• Molecules and Cells
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• v.38 no.10
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• pp.829-835
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• 2015

It has been suggested that AUXIN BINDING PROTEIN 1 (ABP1) functions as an apoplastic auxin receptor, and is known to be involved in the post-transcriptional process, and largely independent of the already well-known SKP-cullin-F-box-transport inhibitor response (TIR1) /auxin signaling F-box (AFB) ($SCF^{TIR1/AFB}$) pathway. In the past 10 years, several key components downstream of ABP1 have been reported. After perceiving the auxin signal, ABP1 interacts, directly or indirectly, with plasma membrane (PM)-localized transmembrane proteins, transmembrane kinase (TMK) or SPIKE1 (SPK1), or other unidentified proteins, which transfer the signal into the cell to the Rho of plants (ROP). ROPs interact with their effectors, such as the ROP interactive CRIB motif-containing protein (RIC), to regulate the endocytosis/exocytosis of the auxin efflux carrier PIN-FORMED (PIN) proteins to mediate polar auxin transport across the PM. Additionally, ABP1 is a negative regulator of the traditional $SCF^{TIR1/AFB}$ auxin signaling pathway. However, Gao et al. (2015) very recently reported that ABP1 is not a key component in auxin signaling, and the famous abp1-1 and abp1-5 mutant Arabidopsis lines are being called into question because of possible additional mutantion sites, making it necessary to reevaluate ABP1. In this review, we will provide a brief overview of the history of ABP1 research.

• The Plant Pathology Journal
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• v.24 no.4
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• pp.367-374
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• 2008

The genomes of plants contain more than 600 genes encoding a diverse set of proteases and the subunits of proteasomes. These proteases and proteasomes consist of plant proteolytic systems, which are involved in various cellular metabolic processes. Plant proteolytic systems have been shown to have diverse roles in defense responses, such as execution of the attack on the invading organisms, participation in signaling cascades, and perception of the invaders. In order to provide a framework for illustrating the importance of proteolytic systems in plant defense, characteristics of non-proteasome proteases and the 26S proteasome are summarized. The involvement of caspase-like proteases, saspases, apoplastic proteases, and the 26S proteasome in pathogen defense suggests that plant proteolytic systems are essential for defense and further clarity on the roles of plant proteases in defense is challenging but fundamentally important to understand plant-microbe interactions.

• The Plant Pathology Journal
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• v.26 no.4
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• pp.402-408
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• 2010

Plant matrix metalloproteases (MMPs) are a family of apoplastic metalloproteases closely related to human matrilysins. Up-regulation of Nicotiana benthamiana matrix metalloprotease 1 (NMMP1) expression by treatment with pathogens, ethephon and aging indicates that the gene is related to plant defense and the aging process through ethylene signaling. NMMP1 expression was higher than in normal growth leaves following infection with an incompatible pathogen Pseudomonas syringae pv. tomato T1 or a compatible pathogen P. syringae pv. tabaci and in aged leaves. Transient overexpression of NMMP1 in N. benthamiana leaves lowered the growth of P. syringae pv. tabaci. However, NMMP1-silenced leaves showed increased growth of P. syringae pv. tabaci. These data strongly suggest that NMMP1 in N. benthamiana is a defense related gene, which is positively regulated by ethylene.