The reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a powerful and widely used technique for the measurement of gene expression. Reference genes, which serve as endogenous controls ensure that the results are accurate and reproducible, are vital for data normalization. To bolster the literature on reference gene selection in maize, ten candidate reference genes, including eight traditionally used internal control genes and two potential candidate genes from our microarray datasets, were evaluated for expression level in maize across abiotic stresses (cold, heat, salinity, and PEG), phytohormone treatments (abscisic acid, salicylic acid, jasmonic acid, ethylene, and gibberellins), and different tissue types. Three analytical software packages, geNorm, NormFinder, and Bestkeeper, were used to assess the stability of reference gene expression. The results revealed that elongation factor 1 alpha (EF1α), tubulin beta (β-TUB), cyclophilin (CYP), and eukaryotic initiation factor 4A (EIF4A) were the most reliable reference genes for overall gene expression normalization in maize, while GRP (Glycine-rich RNA-binding protein), GLU1(beta-glucosidase), and UBQ9 (ubiquitin 9) were the least stable and most unsuitable genes. In addition, the suitability of EF1α, β-TUB, and their combination as reference genes was confirmed by validating the expression of WRKY50 in various samples. The current study indicates the appropriate reference genes for the urgent requirement of gene expression normalization in maize across certain abiotic stresses, hormones, and tissue types.

A SOMATIC EMBRYOGENSIS RECEPTOR KINASE (SERK) gene has been linked to somatic embryogenesis in many plant species. We have developed a culture model that enabled investigation of the relationship between embryogenesis and the expression of various ZmSERK genes at different developmental stages and following treatment with hormones. The results indicate that auxin 2,4-dichlorophenoxyacetic acid (2,4-D) enhanced transcription activity of ZmSERK and promoted somatic embryogenesis. The cytokinin 6-benzyladenine (BA) inhibited embryogenesis and reduced the expression of ZmSERK1 and ZmSERK2, but it significantly increased the expression of ZmSERK3. The application of 2, 4-D and BA promoted the transcription of ZmSERK3 and inhibited that of ZmSERK1 and ZmSERK2, suggesting a fine regulation of embryogenesis by ZmSERK. The immature embryo at 12 and 15 days after pollination (DAP) showed the highest competence for embryogenesis and displayed the strongest ZmSERK gene expression, respectively. Based on these observations, we conclude that the expression profiles of ZmSERKs are closely related to hormone signaling and the developmental stages of the embryo during embryogenesis. ZmSERK1 and ZmSERK2 appear to play an important role in maintaining embryogenesis, while ZmSERK3 appears to have a dual role in embryogenesis by modulating its expression level.

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Intermetallic phases have been known to exhibit a wide diversity since Pauling's seminal investigations into NaCd2 in the 1920s that, along with Cd3Cu4 and Mg2Al3, was shown by Samson to crystallize with a giant cubic cell containing >1000 atoms. The concept of structural plasticity – the notion that complex structures emerge from the release of internal stresses that would arise in simpler structures – has recently been used to account for one family of intermetallics, tracing the structures of Ca2Ag7, Ca14Cd51, CaPd5, and CaCd6 to chemical pressure (CP) issues in the CaCu5 type. Here, we extend the ideal of structural plasticity closer to the giant cells elucidated by Pauling and Samson through its application to a series of Mo−Fe−Cr Frank‐Kasper phases. We begin with a DFT‐CP analysis of the MgZn2‐type phase MoFe2, which serves as a parent structure to μ‐Mo6Fe7 and χ‐Mo5Cr6Fe18. The analysis reveals negative CPs around the Mo atoms arising from collisions between the Fe atoms. Tighter Mo coordination is provided in the μ‐ or χ‐phases by substituting some of the Friauf polyhedra of MoFe2 with either μ‐ and χ‐phase units, resulting in layers or blocks of Laves‐like connectivity. Sites preferences in the μ‐phase and the role of Cr substitution in the χ‐phase are explained through the dual lenses of CP and electronegativity. Parallels to the features of NaCd2 hint that such giant‐unit‐celled intermetallics can represent striking manifestations of structural plasticity.

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