APETALA2 control of barley internode elongation

Abstract

Many plants dramatically elongate their stems during flowering, yet how this response is coordinated with the reproductive phase is unclear. We demonstrate that microRNA (miRNA) control of APETALA2 ( AP2 ) is required for rapid, complete elongation of stem internodes in barley, especially of the final ‘peduncle’ internode directly underneath the inflorescence. Disrupted miR172 targeting of AP2 in the Zeo1.b barley mutant caused lower mitotic activity, delayed growth dynamics and premature lignification in the peduncle leading to fewer and shorter cells. Stage- and tissue-specific comparative transcriptomics between Zeo1.b and its parent cultivar showed reduced expression of proliferation-associated genes, ectopic expression of maturation-related genes and persistent, elevated expression of genes associated with jasmonate and stress responses. We further show that applying methyl jasmonate (MeJA) phenocopied the stem elongation of Zeo1.b , and that Zeo1.b itself was hypersensitive to inhibition by MeJA but less responsive to promotion by gibberellin. Taken together, we propose that miR172-mediated restriction of AP2 may modulate the jasmonate pathway to facilitate gibberellin-promoted stem growth during flowering.

A Novel AP2/ERF Transcription Factor, OsRPH1, Negatively Regulates Plant Height in Rice

“…A total of 170 AP2/ERF genes have been identified in rice genome, and several AP2/ERF members play roles in controlling plant growth and development via integrating different phytohormonal signals (Xu et al, 2006;Fukao and Bailey-Serres, 2008;Yaish et al, 2010;Qi et al, 2011). miR172-mediated HvAP2 controls internode elongation in barley (Patil et al, 2019). However, most of the rice AP2/ERF members have not been studied to date.…”

Besides and beyond Flowering: Other Roles of EuAP2 Genes in Plant Development

“…Interestingly, lignin deposition also appears to be higher in OE-SNB AZ compared to wild type [91]. Overexpression of HvAP2 also results in over deposition of lignin in barley peduncle [83]. Therefore euAP2 genes may be important regulators of lignin synthesis and deposition throughout the plant.…”

“…Patil et al [83] recently reported that plant height is repressed in Zeo1.b barley mutants compared to wild type. Zeo1.b plants overexpress HvAP2 because they possess an allele of HvAP2 with a single nucleotide polymorphism (SNP) in the miR172 binding site, and are, therefore, resistant to miR172 regulation [68].…”

“…Zeo1.b plants overexpress HvAP2 because they possess an allele of HvAP2 with a single nucleotide polymorphism (SNP) in the miR172 binding site, and are, therefore, resistant to miR172 regulation [68]. Patil et al [83] showed that by seven weeks after planting, the height of Zeo1.b plants was only about 50% of the height of wild-type plants. Their analyses indicate that the reduced plant height in Zeo1.b may be attributed to fewer internodes and less number of cells in the peduncle compared to wild type.…”

Besides and Beyond Flowering: Other Roles of euAP2 Genes in Plant Development

“…Interestingly, lignin deposition also appears to be higher in OE-SNB AZ compared to wild type [88]. Overexpression of HvAP2 also results in over deposition of lignin in barley peduncle [107]. Therefore euAP2 genes may be important regulators of lignin synthesis and deposition throughout the plant.…”