Role of ISE2 RNA helicase in chloroplast RNA processing and its relation to PD regulation

CARLOTTO, NICOLAS; WIRTH SONIA; FURMAN, NICOLÁS; ARIEL FEDERICO; CRESPI MARTIN; KOBAYASHI, KEN

Foz do Iguacu

Congreso; 11th International Congress of Plant Molecular Biology; 2015

The Brazilian Genetics Society, SBG

Retrograde signaling from chloroplast to nucleus plays an important role in plasmodesmata (PD) regulation. The ISE2 protein (Increased Size Exclusion Limit 2) is a nuclear-encoded chloroplast-targeted DEVH-box RNA helicase whose mutation shows increased PD aperture during embryogenesis, altered expression of photosynthetic genes and decreased accumulation of photosynthetic pigments in Arabidopsis thaliana. Using Ise2 mutants and ISE2-silenced plants, we found defective splicing of group II intron-containing plastidic RNAs compromising plastid viability. Furthermore, RNA immunoprecipitation indicated that ISE2 binds in vivo to several plastidic intron-containing RNAs. We also determined that the clpr2 mutant (defective in a nucleus-encoded subunit of the plastidic Clp protease system) also exhibited abnormal PD function during embryogenesis, supporting the idea that proper RNA processing in chloroplasts is required for normal PD mediated cell-cell communication in plants. To further test the role of retrograde signaling to the nucleus during PD regulation, we selected other nucleus-encoded chloroplast-targeted genes with plastidic RNA processing functions to make virus-induced gene silencing (VIGS) vectors. We will use the silenced leaves of Nicotiana benthamiana to study the knocking-down effect of these candidate genes on PD function by measuring the spreading rate of soluble GFP.