The small auxin-up RNA OsSAUR45 affects auxin synthesis and transport in rice.

KEY MESSAGE: This research is the first to demonstrate that OsSAUR45 is involved in plant growth though affecting auxin synthesis and transport by repressing OsYUCCA and OsPIN gene expression in rice. Small auxin-up RNAs (SAURs) comprise a large multigene family and are rapidly activated as part of the primary auxin response in plants. However, little is known about the role of SAURs in plant growth and development, especially in monocots. Here, we report the biological function of OsSAUR45 in the model plant rice (Oryza sativa). OsSAUR45 is expressed in a tissue-specific pattern and is localized to the cytoplasm. Rice lines overexpressing OsSAUR45 displayed pleiotropic developmental defects including reduced plant height and primary root length, fewer adventitious roots, narrower leaves, and reduced seed setting. Auxin levels and transport were reduced in the OsSAUR45 overexpression lines, potentially because of decreased expression of Flavin-binding monooxygenase family proteins (OsYUCCAs) and PIN-FORMED family proteins (OsPINs). Exogenous auxin application rapidly induced OsSAUR45 expression and partially restored the phenotype of rice lines overexpressing OsSAUR45. These results demonstrate that OsSAUR45 is involved in plant growth by affecting auxin synthesis and transport through the repression of OsYUCCA and OsPIN gene expression in rice.

Real-time kinetics of cadmium transport and transcriptomic analysis in low cadmium accumulator Miscanthus sacchariflorus.

MAIN CONCLUSION: The molecular mechanism of low Cd influxes and accumulation in Miscanthus sacchariflorus is revealed by RNA sequencing technique. Soil cadmium (Cd) pollution has posed a serious threat to our soil quality and food security as well as to human health. Some wild plants exhibit high tolerance to heavy metals stress. However, mechanisms of Cd tolerance of wild plants remain to be fully clarified. In this study, we found that two Miscanthus species, Miscanthus (M.) sacchariflorus and M. floridulus, showed different Cd-tolerant mechanisms. M. sacchariflorus accumulated less Cd in both root and leaf by limiting Cd uptake from root and showed superior Cd tolerance, while M. floridulus not only absorbs more Cd from root but also transports more Cd to shoot. To investigate the molecular mechanism of different Cd uptake patterns in the two Miscanthus species, we analyzed the transcriptome of M. sacchariflorus and identified transcriptional changes in response to Cd in roots by high-throughput RNA-sequencing technology. A total of 92,985 unigenes were obtained from M. sacchariflorus root cDNA samples. Based on the assembled de novo transcriptome, 681 DEGs which included 345 upregulated and 336 downregulated genes were detected between two libraries of untreated and Cd-treated roots. Gene ontology (GO) and pathway enrichment analysis revealed that upregulated DEGs under Cd stress are predominately involved in metabolic pathway, starch and sucrose and biosynthesis of secondary metabolites and metal ion transporters. Quantitative RT-PCR was employed to compare the expression levels of some metal transport genes in roots of two Miscanthus species, and the genes involved in Cd uptake from root and transfer from root to shoot were extremely different. The results not only enrich genomic resource but also help to better understand the molecular mechanisms of Cd accumulation and tolerance in wild plants.