Study of Chinese Medicine Protopine on Attenuating Tau Pathology in Alzheimer's Disease: the Roles of Histone Deacetylase 6

In eukaryotic organisms, post-transcriptional mechanisms such as alternative splicing (AS) generate multiple mRNA isoforms from single template DNA. Using this strategy, eukaryotes are able to make full use of a limited genome to generate a diversified proteome for carrying out a variety of functions. As a consequence, AS contributes to the flexibility of organisms under varied physiological conditions. However, which splicing isoforms will be generated or translated into proteins, and whether the resulted proteoforms can display distinct functions are largely unknown.

We have identified global changes of both AS transcripts and proteins under normal conditions or in response to abscisic acid (ABA) treatment by using parallel approaches of short-read RNA sequencing, single molecule long-read RNA sequencing and proteomic identification in Arabidopsis. Approximately 83.4% of multi-exonic genes have been observed to contain splicing isoforms. ABA treatment increased the number of non-conventional splicing sites among these ABA-regulated AS isoforms. Thus splicing factors, as essential components in the spliceosome, play pivotal roles in response to developmental cues and environmental changes. In addition, we also found that the expression of five isoforms of a serine/arginine-rich splicing factor, SR184, was altered under ABA treatment. These five isoforms exhibited three different subcellular locations and the mutant of this gene was sensitive to ABA treatment. These findings raise the intriguing possibility that SR184 may participate in ABA-mediated stress responses. Isoforms potentially encode five proteins that might have distinct functions in response to ABA-regulated splicing changes.

In this proposed study, we will further characterize the phenotypic differences under stress treatments using Arabidopsis genetic materials including knock-out mutants for all the five splicing isoforms, knock-out mutants, overexpression and complement lines for each SR184 splicing isoform. We will analyse the spatio-temporal expression pattern of these splicing isoforms at both the transcriptional and protein levels. The subcellular localization of each SR184 splicing isoform will be further investigated. Subsequently, the AS pattern and splicing site usage will be compared among the above mentioned Arabidopsis genetic materials under normal conditions and in response to stress treatments. To further reveal the underlying mechanism of AS regulation, crosstalk between alternative splicing and transcriptional control of ABA signalling will be further investigated using mutants of ABA-responsive transcription factors. In addition, we will continuously screen and validate the protein partners of SR184 and its splicing isoforms. Our study should provide new understanding into the diverse responsive mechanisms of plant splicing factors and AS regulation in ABA-mediated stress responses.