TITLE:
Elaborating the Functional Roles of a Leucine-Rich Repeat Protein from Arabidopsis thaliana
AUTHORS:
Angela Sibanda-Makuvise, Tshegofatso B. Dikobe, Katlego S. Sehlabane, Enetia D. Bobo, Neo M. Mametja, Mutsa M. Takundwa, David T. Kawadza, Thembekile Ncube, Oziniel Ruzvidzo
KEYWORDS:
Disease Resistance, Adenylyl Cyclase, R-Proteins, AtLRR, Plant Development, Plant Reproduction
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.13 No.11,
November
30,
2022
ABSTRACT: Plants, just like any other living organism, naturally get attacked by
various pathogenic microorganisms such as bacteria, fungi and viruses. However,
unlike animals that utilize their specialized circulatory macrophage system to
protect themselves, plants instead use a multi-layered complex system termed the
plant innate immunity, which recognizes pathogens and transducing downstream defense
responses. They have developed a unique type of trans-membrane receptors or R proteins, which
extracellularly, are capable of recognizing pathogen-associated molecular
patterns (PAMP) such as flagellin and chitin, while intracellularly, they
activate their harbored nucleotide cyclases (NCs) such as adenylyl cyclases
(ACs), to generate second messenger molecules such as 3’,5’-cyclic adenosine
monophosphate (cAMP), which then propagates and magnifies the defense response.
To date, only a single R protein from Arabidopsis thaliana (AtLRR) has
been shown to possess AC activity as well as having the ability to defend
plants against infection by biotrophic and hemi-biotrophic pathogens.
Therefore, in order to further broaden information around the functional roles
of this protein (AtLRR), we explored it further, using an array of web-based
tools or bioinformatics. These included structural analysis, anatomical
expression analysis, developmental expression analysis, co-expression analysis,
functional enrichment analysis, stimulus-specific
expression analysis and promoter analysis. Findings from structural analysis
showed that AtLRR is a multi-domain, trans-membrane molecule that is
multi-functional, and thus consistent with all known R-proteins. Findings from
anatomical and developmental expression analyses showed that AtLRR is mostly
expressed in pollen grains and flowers, senescing leaves as well as during the
development of seeds, shoots, roots, seedlings, leaves, flowers, and siliques,
linking it to the three key plant physiological processes of reproduction,
defense and development respectively. Lastly, findings from co-expression,
functional enrichment, stimulus-specific expression and promoter analyses,
showed that AtLRR is mostly co-expressed with several other proteins linked to
disease resistance, plant reproduction and plant development. Activities and
functions of such protein are also commonly regulated by cAMP via a common
W-box promoter. So, all in all, our study managed to establish that besides
being strongly involved in disease resistance against biotrophic and
hemi-biotrophic pathogens, AtLRR also plays key roles in plant development
(seed, shoot, root, seedling, leaf, and silique development) and reproduction (flowering, and pollen tube growth
and re-orientation), whereby it effects its functions via a W-box or WRKY
transcription factor, TTGACY, mediated by cAMP.