Transformation of Long-Lived Albino Epipremnum aureum 'Golden Pothos' and Restoring Chloroplast Development

Integrated genomic and transcriptomic analysis reveals the mechanisms underlying leaf variegation in 'Gonggan' mandarin

BACKGROUND

The 'Gonggan' mandarin, an elite local cultivar from Zhaoqing City, Guangdong Province, combines the qualities of mandarin and sweet orange. A leaf-variegated mutant enhances its ornamental and economic value, providing an excellent model for studying chloroplast development and photosynthetic pigment metabolism in citrus.

RESULTS

We found that, in this variegated mutant, chloroplasts are severely deficient or absent in mesophyll cells. Physiological assessments revealed lower levels of chlorophyll, carotenoids, net photosynthetic rate (Pn), and stomatal conductance (Gs), alongside significantly higher non-photochemical quenching (NPQ) and the non-photochemical quenching coefficient (qN), reflecting increased photoprotective energy dissipation. To uncover the molecular basis of leaf variegation, high-quality genome assemblies and transcriptomes were generated for both the normal and variegated 'Gonggan' mandarin, enabling comparative multi-omics analysis. Key genes involved in chloroplast development, such as TOC159, PDV2, THA8, and SIG5, were downregulated in the variegated leaves. Similarly, structural genes linked to chlorophyll degradation, including CLH2, SGR, NOL, and NYC1, exhibited altered expression. Downregulation of transcription factors GLK, GNC, and GNC-LIKE (GNL), known regulators of chloroplast development and chlorophyll biosynthesis, was also observed.

CONCLUSIONS

These findings suggest that disrupted expression of critical genes impacts chloroplast development and pigment metabolism, causing the leaf variegation phenotype. Overall, this study lays a foundation for functional genomics research and potential germplasm improvement of 'Gonggan' mandarin, and provides new insights into the mechanisms driving color variation in citrus.

Chloroplast Functionality at the Interface of Growth, Defense, and Genetic Innovation: A Multi-Omics and Technological Perspective

Chloroplasts are important in plant growth, development, and defense mechanisms, making them central to addressing global agricultural challenges. This review explores the multi-faceted contributions of chloroplasts, including photosynthesis, hormone biosynthesis, and stress signaling, which orchestrate the trade-off between growth and defense. Advancements in chloroplast genomics, transcription, translation, and proteomics have deepened our understanding of their regulatory functions and interactions with nuclear-encoded proteins. Case studies have demonstrated the potential of chloroplast-targeted strategies, such as the expression of elongation factor EF-2 for heat tolerance and flavodiiron proteins for drought resilience, to enhance crop productivity and stress adaptation. Future research directions should focus on the need for integrating omics data with nanotechnology and synthetic biology to develop sustainable and resilient agricultural systems. This review uniquely integrates recent advancements in chloroplast genomics, transcriptional regulation, and synthetic biology to present a holistic perspective on optimizing plant growth and stress tolerance. We emphasize the role of chloroplast-driven trade-off in balancing growth and immunity, leveraging omics technologies and emerging biotechnological innovations. This comprehensive approach offers new insights into sustainable agricultural practices, making it a significant contribution to the field.

Tissue Culture in Ornamentals: Cultivation Factors, Propagation Techniques, and Its Application

Ornamentals come in a variety of shapes, sizes, and colors to suit a wide range of climates, landscapes, and gardening needs. Compared to demand, a shortage of plant materials and diversity force the search for solutions for their constant acquisition and improvement to increase their commercial value, respectively. In vitro cultures are a suitable solution to meet expectations using callus culture, somatic embryogenesis, protoplast culture, and the organogenesis of protocorm-like bodies; many of these techniques are commercially practiced. Factors such as culture media, explants, carbohydrates, plant growth regulators, and light are associated with the success of in vitro propagation. Techniques, especially embryo rescue and somatic hybridization, are widely used to improve ornamentals. The development of synthetic seed allows season-independent seed production and preservation in the long term. Despite the advantages of propagation and the improvement of ornamentals, many barriers still need to be resolved. In contrast to propagation and crop developmental studies, there is also a high scope for molecular studies, especially epigenetic changes caused by plant tissue culture of ornamentals. In this review, we have accumulated and discussed an overall update on cultivation factors, propagation techniques in ornamental plant tissue culture, in vitro plant improvement techniques, and future perspectives.

Mutation in Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase Gene ZmCRD1 Causes Chlorophyll-Deficiency in Maize

Chlorophyll molecules are non-covalently associated with chlorophyll-binding proteins to harvest light and perform charge separation vital for energy conservation during photosynthetic electron transfer in photosynthesis for photosynthetic organisms. The present study characterized a pale-green leaf (pgl) maize mutant controlled by a single recessive gene causing chlorophyll reduction throughout the whole life cycle. Through positional mapping and complementation allelic test, Zm00001d008230 (ZmCRD1) with two missense mutations (p.A44T and p.T326M) was identified as the causal gene encoding magnesium-protoporphyrin IX monomethyl ester cyclase (MgPEC). Phylogenetic analysis of ZmCRD1 within and among species revealed that the p.T326M mutation was more likely to be causal. Subcellular localization showed that ZmCRD1 was targeted to chloroplasts. The pgl mutant showed a malformed chloroplast morphology and reduced number of starch grains in bundle sheath cells. The ZmCRD1 gene was mainly expressed in WT and mutant leaves, but the expression was reduced in the mutant. Most of the genes involved in chlorophyll biosynthesis, chlorophyll degradation, chloroplast development and photosynthesis were down-regulated in pgl. The photosynthetic capacity was limited along with developmental retardation and production reduction in pgl. These results confirmed the crucial role of ZmCRD1 in chlorophyll biosynthesis, chloroplast development and photosynthesis in maize.