Project description:Innovative strategies for increasing the yield of rice, the staple food for more than half of the global population, are needed to keep pace with the expected worldwide population increase, and sustainably forefront the challenges posed by climate change. Traditionally, in Southern-East Asian countries, rice farming benefits from the use of Azolla spp., either as green manure or as co-cultivated plants, for the supply of nitrogen. Azolla spp. are ferns that, in virtue of their symbiosis with the nitrogen-fixing cyanobacterium Trichormus azollae, fix atmospheric nitrogen and release it to the environment upon decomposition of their biomass. However, if and to what extent actively growing Azolla plants impact on the development of co-cultivated rice plantlets remains to be understood. To address this point here we employed an experimental model to follow the growth and development of roots and aerial organs of rice seedlings when co-cultivated with Azolla filiculoides. We show that actively growing A. filiculoides plants alter the architecture of the roots, the transcriptome of the roots, and the hormonal profiles of both roots and leaves.
Project description:RNA editing is essential for processing transcripts in plant chloroplasts and mitochondria. Levels of RNA editing vary between lineages, but some hornworts, lycophytes and ferns have an extraordinary abundance of RNA editing. A feature of ‘hyper-editing’ species is the prevalence of RNA editing events which influence translation by affecting start codons and stop codons via C-to-U editing and U-to-C editing respectively. These ‘translationally significant’ RNA editing events may play roles in regulating organelle gene expression. To investigate the importance of translationally significant RNA editing events, we generated DNA and RNA sequence libraries for four Salviniales water ferns: Azolla rubra, Azolla pinnata, Marsilea mutica and Salvinia molesta. We assembled chloroplast genomes, mitochondrial genes and transcriptomes, and identified RNA editing sites and candidate RNA editing factors. We re-analysed sequence data of Azolla filiculoides and conducted a comparative analysis of RNA editing in chloroplasts and mitochondrial transcripts. Estimates of pyrimidine transition rates show that translationally significant RNA editing sites are more conserved than other non-synonymous editing sites, suggesting an emergent role in organelle gene expression that is not selectively neutral. Shotgun proteomics of Marsilea mutica chloroplast thylakoid fractions verified the expected consequences of RNA editing on translation of chloroplast transcripts and implies that mechanisms exist to avoid translation of partially edited transcripts. Start codon editing may be one of those mechanisms.
