Poplar PtabZIP1 positively regulates lateral root formation and flavonoid synthesis and enhance biomass growth under drought
Madhumita Dash, Yordan S. Yordanov, Tatyana Georgieva, Timothy J. Tschaplinski, Elena Yordanova, and Victor Busov
04 November 2016, The Plant Journal 89(4): 692-705; DOI: 10.111/tpj.13413
Developing drought-resistance varieties is a major goal for bioenergy crops, such as poplar (Populus), which will be grown on marginal lands with little or no water input. Root architecture can affect drought-resistance, but few genes that affect root architecture in relation to water availability have been identified. Here, using activation tagging in the prime bioenergy crop poplar, we have identified a mutant that overcomes the block of lateral root (LR) formation under osmotic stress. Positioning of the tag, validation of the activation and recapitulation showed that the phenotype is caused by the poplar PtabZIP1-like (PtabZIP1L) gene with highest homology to bZIP1 fromArabidopsis. PtabZIP1L is predominantly expressed in roots, particularly in zones where lateral root primordia (LRP) initiate and LR differentiate and emerge. Transgenics overexpressing PtabZIP1L showed precocious LRP and LR development, while PtabZIP1L suppression significantly delayed both LRP and LR formation. Transgenic overexpression and suppression of PtabZIP1L also resulted in modulation of key metabolites like proline, asparagine, valine and several flavonoids. Consistently, expression of both of the poplar Proline Dehydrogenase orthologs and two of the Flavonol Synthases genes was also increased and decreased in overexpressed and suppressed transgenics, respectively. These findings suggest that PtabZIP1L mediates LR development and drought resistance through modulation of multiple metabolic pathways.
Dash, M., Yordanov, Y. S., Georgieva, T., Tschaplinski, T. J., Yordanova, E. and Busov, V. (2016), Poplar PtabZIP1-like enhances lateral root formation and biomass growth under drought stress. Plant J. Accepted Author Manuscript. doi:10.1111/tpj.13413