Interaction of hormonal and two component signaling pathways - regulatory modules determining differentiation of transfer tissues in barley
Plant Physiology
Final Report Abstract
Assimilate supply to reproductive organs has a major impact on yield in cereal crops like barley and wheat by affecting grain number and grain size. The development of grains is associated with differentiation of distinct transfer tissues for nutrient uptake in filial grain organs, particularly the endosperm. Identification of key components and regulatory networks triggering differentiation of transfer tissues is a prerequisite for improvement of yield potential. Tissue-specific mRNA-sequencing identified two-component signaling (TCS) phosphorelays as major signal transduction pathway in differentiating endosperm transfer cells (ETCs) of barley. Histidine kinase1 (HvHK1) was identified as a receptor component with a unique expression in the syncytial endosperm domain at the maternalfilial boundary of grains. Knockdown of HvHK1 by RNAi impairs cell specification in the central ETC region, development of the transfer cell morphology and produces smaller grains with reduced starch content. A gene regulatory network of HvHK1 predicted genes involved in auxin signaling, TCS phosphorelays and protein degradation as potential targets of HvHK1 during ETC specification. TALEN-mediated gene modification of type-C response regulator HvRR15 and/or gene copies induced strong endosperm-specific phenotypes with disrupted central endosperm, poorly developed ETCs and abnormal aleurone differentiation in the lobe region. High-resolution transcriptome profiling implies that phosphorelays impact differentiation of other transfer tissues in grains and barley spikes. On basis of that, mutants of further TCS candidate genes have been generated by the CRISPR/Cas9-technology to establish new models for functional studies in planta. First histological analyses of etr1- and rr10-mutants show promising grain-specific phenotypes with defects in endosperm differentiation. Genetic confirmation and detailed phenotypic analyses of mutant plants in the next generations will decipher the function in grain/spike development. Co-localization of TCS gene cluster in the barley genome with QTLs for different agronomic traits further support the assumption that TCS phosphorelays have an impact on yield potential in barley.
Publications
- (2018) Laser capture microdissection-based RNA-Seq of barley grain tissues. Methods Mol Biol 1723: 397-409
Brandt, R., Mascher, M. & Thiel, J.
(See online at https://doi.org/10.1007/978-1-4939-7558-7_23)
