Amyloid precursor protein and growth-associated protein 43 expression in brain white matter and spinal cord tissues in a rat model of experimental autoimmune encephalomyelitis

Studies have demonstrated that amyloid precursor protein （APP） expression increases in multiple sclerosis tissues during acutely and chronically active stages. To determine the relationship between axonal injury and regeneration in multiple sclerosis, an animal model of experimental autoimmune encephalomyelitis was induced using different doses of myelin basic protein peptide. APP and growth-associated protein 43 （GAP-43）, which is considered a specific marker of neural regeneration, were assessed by western blot analysis. Expression of APP and GAP-43, as well as the correlation between these two proteins, in brain white matter and spinal cord tissues of experimental autoimmune encephalomyelitis rats at different pathological stages was analyzed. Results showed that APP and GAP-43 expression increased during the acute stage and decreased during remission, with a positive correlation between APP and GAP-43 expression in brain white matter and spinal cord tissues. These results suggest that APP and GAP-43 could provide nutritional and protective effects on damaged neurons.

Phytochrome B interacts with SWC6 and ARP6 to regulate H2A.Z deposition and photomorphogensis in Arabidopsis

Light serves as a crucial environmental cue which modulates plant growth and development, and which is controlled by multiple photoreceptors including the primary red light photoreceptor,phytochrome B(phyB). The signaling mechanism of phyB involves direct interactions with a group of basic helix-loop-helix(bHLH) transcription factors, PHYTOCHROME-INTERACTING FACTORS(PIFs), and the negative regulators of photomorphogenesis, COP1 and SPAs. H2 A.Z is an evolutionarily conserved H2 A variant which plays essential roles in transcriptional regulation. The replacement of H2 A with H2 A.Z is catalyzed by the SWR1 complex. Here, we show that the Pfr form of phyB physically interacts with the SWR1 complex subunits SWC6 and ARP6. phyB and ARP6 coregulate numerous genes in the same direction,some of which are associated with auxin biosynthesis and response including YUC9, which encodes a rate-limiting enzyme in the tryptophandependent auxin biosynthesis pathway. Moreover,phyB and HY5/HYH act to inhibit hypocotyl elongation partially through repression of auxin biosynthesis. Based on our findings and previous studies, we propose that phyB promotes H2 A.Z deposition at YUC9 to inhibit its expression through direct phyB-SWC6/ARP6 interactions,leading to repression of auxin biosynthesis, and thus inhibition of hypocotyl elongation in red light.

Arabidopsis cryptochrome 1 promotes stomatal development through repression of AGB1 inhibition of SPEECHLESS DNA-binding activity

Cryptochromes are blue light photoreceptors that mediate various light responses in plants and mammals. The heterotrimeric G-protein is known to regulate various physiological processes in plants and mammals. In Arabidopsis, cryptochrome 1(CRY1) and the G-protein β subunit AGB1 act antagonistically to regulate stomatal development.The molecular mechanism by which CRY1 and AGB1 regulate this process remains unknown.Here, we show that Arabidopsis CRY1 acts partially through AGB1, and AGB1 acts through SPEECHLESS(SPCH), a master transcription factor that drives stomatal initiation and proliferation, to regulate stomatal development. We demonstrate that AGB1 physically interacts with SPCH to block the b HLH DNA-binding domain of SPCH and inhibit its DNA-binding activity. Moreover, we demonstrate that photoexcited CRY1 represses the interaction of AGB1 with SPCH to release AGB1 inhibition of SPCH DNA-binding activity, leading to the expression of SPCH-target genes promoting stomatal development. Taken together, our results suggest that the mechanism by which CRY1 promotes stomatal development involves positive regulation of the DNA-binding activity of SPCH mediated by CRY1 inhibition of the AGB1-SPCH interaction. We propose that the antagonistic regulation of SPCH DNA-binding activity by CRY1 and AGB1 may allow plants to balance light and G-protein signaling and optimize stomatal density and pattern.

The involvement of the N-terminal PHR domain of Arabidopsis cryptochromes in mediating light signaling

Light is a key environmental cue that fundamentally regulates all aspects of plant growth and development,which is mediated by the multiple photoreceptors including the blue light photoreceptors cryptochromes(CRYs).In Arabidopsis,there are two well-characterized homologous CRYs,CRY1 and CRY2.Whereas CRYs are flavoproteins,they lack photolyase activity and are characterized by an Nterminal photolyase-homologous region(PHR)domain and a C-terminal extension domain.It has been established that the C-terminal extension domain of CRYs is involved in mediating light signaling through direct interactions with the master negative regulator of photomorphogenesis,COP1.Recent studies have revealed that the N-terminal PHR domain of CRYs is also involved in mediating light signaling.In this review,we mainly summarize and discuss the recent advances in CRYs signaling mediated by the N-terminal PHR domain,which involves the N-terminal PHR domain-mediated dimerization/oligomerization of CRYs and physical interactions with the pivotal transcription regulators in light and phytohormone signaling.