''AvrPphB SUSCEPTIBLE 1/PBS1'' is a

protein kinase A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them ( phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a f ...

acting upon

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

and

threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form when dissolved in water), a carboxyl group (which is in the deprotonated −COO− ...

. . . .Q9FE20
/ref> It is a receptor-like cytoplasmic kinase, of Subfamily VII. It is the guardee of '' RESISTANCE TO PSEUDOMONAS SYRINGAE 5/RPS5''. PBS1 is cleaved by an

effector Effector may refer to: *Effector (biology), a molecule that binds to a protein and thereby alters the activity of that protein * ''Effector'' (album), a music album by the Experimental Techno group Download * ''EFFector'', a publication of the El ...

, AvrPphB, used by ''Pseudomonas syringae'' pv. ''phaseolicola'', serving as an immunological

decoy A decoy (derived from the Dutch ''de'' ''kooi'', literally "the cage" or possibly ''eenden kooi'', " duck cage") is usually a person, device, or event which resembles what an individual or a group might be looking for, but it is only meant to ...

to signal RPS5 that an attack is underway as reviewed by Kourelis et al. 2016.

Evolutionary history

Targets are under so much pressure from effectors that McDowell & Simon 2006 expected ''PBS1'' to experience diversifying selection. They looked forward to results finding little sequence affinity, an entire family of ''PBS1''s, and radiation across descendant plant species. However just a few years later ''PBS1'' was demonstrated by Caldwell and Michelmore 2009 to be one of the most conserved proteins in all

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s. Further, they found it to be so widespread that it must have yet-undiscovered function(s): It is found widely even in taxa with no RPS5 guard. They speculate that these other functions are so vital that PBS1 is being prevented from otherwise adapting to effectors - thus possibly dumping that evolutionary pressure onto the nucleotide-binding leucine-rich repeat receptors guarding it instead. They also found this to make PBS1 an even more useful modifiable immune decoy, as it is recognized by a wider array of

convergently evolved Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

immune proteins than just RPS5.

Orthologs

One model and many economic plants are known to have multiple

ortholog Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speci ...

s per genome: * ''At''PBS1 - in the model ''

Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally ...

'' :* ''At''PBS1 - with a 5-

Alanine Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...

insertion to produce a gape in the cleavage site, falsely mimicking constant cleavage by the effector * ''Gm''PBS1 - in ''

Glycine max The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source of f ...

'' :* ''Gm''PBS1–1 ::* ''Gm''PBS1–1 - same results as the 5xAla ''At''PBS1 above :* ''Gm''PBS1 - against

Soybean Mosaic Virus Soybean mosaic virus (SMV) is a member of the plant virus genus ''Potyvirus'' (family Potyviridae). It infects mainly plants belonging to the family Fabaceae but has also been found infecting other economically important crops. SMV is the cause o ...

* PBS1 - against the Type-III effector of AvrRpt2 produced by '' P. syringae'' * PBS1 - against the Nla protease produced by the Tobacco Etch Virus (TEV) * PBS1 - against the Nla protease produced by the Turnip Mosaic Virus (TuMV)

Future research

Indiana University Indiana University (IU) is a state university system, system of Public university, public universities in the U.S. state of Indiana. The system has two core campuses, five regional campuses, and two regional centers under the administration o ...

(home of Pottinger and Innes) is prosecuting a family of patents for the RPS5-PBS1 decoy system. In the future it is expected that modified PBS1 decoys will become cheaper and easier to make as unrelated molecular genetics technologies improve. This system will only be deployable against effectors which act intracellularly within the host, as PBS1 is not located in any extracellular locations. The determination of the structure of ZAR1 has been useful in understanding NLRs in general, and that information will continue to be applied to understand and develop PBS1s.

References

{{Plant-disease-stub Plant genes Arabidopsis thaliana genes