ZmGI2 regulates flowering time through multiple flower development pathways in maize.

GIGANTEA (GI) encodes a component of the circadian clock core oscillator and has been identified as a regulatory pathway of the circadian rhythm and photoperiodic flowering in model plants. However, the regulatory pathway of GI affecting flowering time is unknown in maize. Here, we identified that the zmgi2 mutant flowered earlier than the wild type under long day (LD) conditions, whereas the difference in flowering time was not apparent under short day (SD) conditions. The 24 h optimal expression of the gene in the stem apex meristems (SAM) appeared at 9 h after dawn under LD conditions and at 11 h after dawn under SD conditions. DAP-Seq and RNA-Seq further revealed that ZmGI2 delays flowering by directly binding to the upstream regions of ZmVOZs, ZmZCN8 and ZmFPF1 to repress the expression of these genes and by directly binding to the upstream regions of ZmARR11, ZmDOF and ZmUBC11 to promote the expression of these genes. The genetic and biochemical evidence suggests a model for the potential role of ZmGI2 in regulating the flowering time-dependent photoperiodic pathway. This study provides novel insights into the function of ZmGIs in maize and further demonstrates their potential importance for floral transition. These results contribute to a comprehensive understanding of the molecular mechanisms and regulatory networks of GI transcription factors in regulating flowering time in maize.

Research on the deformation law for flat rolling of a core filled tube based on the slab method.

The deformation law for axisymmetric deformation during the drawing of a core filled tube (CORFT) has been studied. However, the results of such studies could not be used in the flat rolling process of the CORFT, which is a plan deformation condition. In this paper, the inner core material and outer steel tube were successively analyzed based on the slab method during the flat rolling process (plan deformation) of the CORFT, and equations for wall thickness, core density, and roll force have been developed. The theoretical results solved by the developed equations were compared with the experimental results, revealing adequate accuracy for engineering requirements. The influences of rolling parameters on the roll force and the ultimate value of the relative density of the core material were studied, and the limiting condition for a larger roll force or higher value for relative density was obtained.

ZmDREB2A regulates ZmGH3.2 and ZmRAFS, shifting metabolism towards seed aging tolerance over seedling growth.

Seed aging tolerance and rapid seedling growth are important agronomic traits for crop production; however, how these traits are controlled at the molecular level remains largely unknown. The unaged seeds of two independent maize DEHYDRATION-RESPONSIVE ELEMENT-BINDING2A mutant (zmdreb2a) lines, with decreased expression of GRETCHEN HAGEN3.2 (ZmGH3.2, encoding indole-3-acetic acid [IAA] deactivating enzyme), and increased IAA in their embryo, produced longer seedling shoots and roots, than the null segregant (NS) controls. However, the zmdreb2a seeds, with decreased expression of RAFFINOSE SYNTHASE (ZmRAFS) and less raffinose in their embryo, exhibit decreased seed aging tolerance, than the NS controls. Overexpression of ZmDREB2A in maize protoplasts increased the expression of ZmGH3.2, ZmRAFS genes and that of a Rennila LUCIFERASE reporter (Rluc) gene, which was controlled by either the ZmGH3.2- or ZmRAFS-promoter. Electrophoretic mobility shift assays and chromatin immunoprecipitation assay quantitative polymerase chain reaction showed that ZmDREB2A directly binds to the DRE motif of the promoters of both ZmGH3.2 and ZmRAFS. Exogenous supplementation of IAA to the unaged, germinating NS seeds increased subsequent seedling growth making them similar to the zmdreb2a seedlings from unaged seeds. These findings provide evidence that ZmDREB2A regulates the longevity of maize seed by stimulating the production of raffinose while simultaneously acting to limit auxin-mediated cell expansion.

ZmDREB1A Regulates RAFFINOSE SYNTHASE Controlling Raffinose Accumulation and Plant Chilling Stress Tolerance in Maize.

Raffinose accumulation is positively correlated with plant chilling stress tolerance; however, the understanding of the function and regulation of raffinose metabolism under chilling stress remains in its infancy. RAFFINOSE SYNTHASE (RAFS) is the key enzyme for raffinose biosynthesis. In this study, we report that two independent maize (Zea mays) zmrafs mutant lines, in which raffinose was completely abolished, were more sensitive to chilling stress and their net photosynthetic product (total soluble sugars and starch) accumulation was significantly decreased compared with controls after chilling stress. A similar characterization of the maize dehydration responsive element (DRE)-binding protein 1A mutant (zmdreb1a) showed that ZmRAFS expression and raffinose content were significantly decreased compared with its control under chilling stress. Overexpression of maize ZmDREB1A in maize leaf protoplasts increased ZmDREB1A amounts, which consequently upregulated the expression of maize ZmRAFS and the Renilla LUCIFERASE (Rluc), which was controlled by the ZmRAFS promoter. Deletion of the single dehydration-responsive element (DRE) in the ZmRAFS promoter abolished ZmDREB1A's influence on Rluc expression, while addition of three copies of the DRE in the ZmRAFS promoter dramatically increased Rluc expression when ZmDREB1A was simultaneously overexpressed. Electrophoretic mobility shift assays and chromatin immunoprecipitation-quantitative PCR demonstrated that ZmDREB1A directly binds to the DRE motif in the promoter of ZmRAFS both in vitro and in vivo. These data demonstrate that ZmRAFS, which was directly regulated by ZmDREB1A, enhances both raffinose biosynthesis and plant chilling stress tolerance.