Elaborating the Functional Roles of a Leucine-Rich Repeat Protein from Arabidopsis thaliana

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.

An enhanced network of energy metabolism,lysine acetylation,and growth-promoting protein accumulation is associated with heterosis in elite hybrid rice

Heterosis refers to the superior performance of a hybrid compared with its parental lines.Although several genetic and molecular models have been proposed to explain heterosis,it remains unclear how hybrid cells integrate complementary gene expression or activity to drive heterotic growth.In this work,we show that accumulation of growth-promoting and energy metabolism proteins,enhanced energy metabolism activities,and increased protein lysine acetylation were associated with superior growth of the panicle meristem in the elite hybrid rice Shanyou 63 relative to its parental varieties.Metabolism of nuclear/cytosolic acetylcoenzyme A was also enhanced in the hybrid,which paralleled increases in histone H3 acetylation to selectively target the expression of growth-promoting and metabolic genes.Lysine acetylation of cellular proteins,including TARGET OF RAPAMYCIN complex 1,ribosomal proteins,and energy metabolism enzymes,was also augmented and/or remodeled to modulate their activities.The data indicate that an enhanced network of energy-producing metabolic activity and growth-promoting histone acetylation/gene expression in the hybrid could contribute to its superior growth rate and may constitute a model to explain heterosis.