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Summary: Callus formation is important for numerous biological processes in plants. Previously, we revealed that the PdeWRKY75–PdeRBOHB module positively regulates hydrogen peroxide (H2O2) accumulation, thereby affecting callus formation in poplar.In this study, we identified and confirmed a transcription factor, PdeERF114, that interacts with PdeWRKY75 both in vitro and in vivo. Gene expression analysis identified both PdeRBOHB and PdeEXPB2 as downstream genes of PdeERF114 and PdeWRKY75. Overexpression (OE) and reduced‐expression (RE) transgenic poplar lines for these four genes were generated, and the observation of callus formation was also performed in all plant materials.We demonstrated that PdeERF114 and PdeWRKY75 formed a protein complex and that this complex could bind W‐Box motifs in the promoters of PdeRBOHB and PdeEXPB2, thereby positively regulating the expression of PdeRBOHB and PdeEXPB2. The OE/RE transgenic lines for these four genes also showed enhanced/reduced callus formation.Overall, we revealed a novel gene regulatory network for the regulation of callus formation in plants that involves four genes and regulates callus formation through two pathways: the accumulation of H2O2 in explants and the relaxation of cell walls. In the future, the four genes could be used to enhance transformation effectiveness in genetic engineering. [ABSTRACT FROM AUTHOR]

Summary: Rice grain is a poor dietary source of zinc (Zn) but the primary source of cadmium (Cd) for humans; however, the molecular mechanisms for their accumulation in rice grain remain incompletely understood.This study functionally characterized a tonoplast‐localized transporter, OsMTP1. OsMTP1 was preferentially expressed in the roots, aleurone layer, and embryo of seeds. OsMTP1 knockout decreased Zn concentration in the root cell sap, roots, aleurone layer and embryo, and subsequently increased Zn concentration in shoots and polished rice (endosperm) without yield penalty. OsMTP1 haplotype analysis revealed elite alleles associated with increased Zn level in polished rice, mostly because of the decreased OsMTP1 transcripts.OsMTP1 expression in yeast enhanced Zn tolerance but did not affect that of Cd. While OsMTP1 knockout resulted in decreased uptake, translocation and accumulation of Cd in plant and rice grain, which could be attributed to the indirect effects of altered Zn accumulation.Our results suggest that rice OsMTP1 primarily functions as a tonoplast‐localized transporter for sequestrating Zn into vacuole. OsMTP1 knockout elevated Zn concentration but prevented Cd deposition in polished rice without yield penalty. Thus, OsMTP1 is a candidate gene for enhancing Zn level and reducing Cd level in rice grains. [ABSTRACT FROM AUTHOR]