Xinchun Lin

Summary: Culm colour is one of the primary traits determining the ornamental value of bamboos. The black pigment shown to accumulate in Phyllostachys nigra was previously characterized as melanin, but the underlying regulatory mechanism for its deposition remains elusive. Herein, metabolomics data show that coumarins serve as precursor substrates for melanization in P. nigra , and RNA‐seq and weighted gene correlation network analysis (WGCNA) revealed that the transcription factor PnMYB4a is integral to coumarin biosynthesis. Overexpression of PnMYB4a promotes coumarin production in both Oryza sativa and Arabidopsis thaliana . Pn4CL4‐2 , a biosynthetic gene involved in coumarin biosynthesis, was identified as a direct target gene of PnMYB4a. Additionally, PnWRKY8 and PnWRKY72‐2 were found to interact with PnMYB4a both in vivo and in vitro . Both PnWRKY8 and PnWRKY72‐2 positively promoted coumarin accumulation in transgenic rice, but they repressed the expression of Pn4CL4‐2 by directly binding to W‐box elements within its promoter. Interestingly, PnMYB4a was found to alleviate the inhibitory effect on Pn4CL4‐2 by forming complexes with both PnWRKY8 and PnWRKY72‐2. Collectively, these findings revealed a PnMYB4a‐PnWRKY8/PnWRKY72‐2 regulatory module involved in the coumarin biosynthetic pathway in P. nigra and provide new insights into the mechanisms of melanization and coloration in bamboo species.

Background: The bamboo species Dendrocalamus × mutatus T.P.Yi & B.X.Li (D. mutatus) holds great economic and ecological importance in China. Although previously D. mutatus was presumed to be a hybrid of Bambusa grandis and Bambusa pervariabilis, its taxonomic status has remained uncertain. Therefore, we combined plastomes and nuclear SSR datasets, in addition to morphological data, to refine our understanding of the taxonomic status of D. mutatus. Results: The chloroplast genome of D. mutatus exhibits a typical quadripartite structure, comprising a large single-copy region (LSC), a small single-copy region (SSC), and two inverted repeat regions (IRa and IRb), containing a total length of 139,432 bp. Comparative genomic analyses revealed extremely high similarity between D. mutatus and D. yunnanicus, differing by only two single-nucleotide polymorphisms (SNPs). In contrast, a greater divergence was observed when compared with D. sikkimensis (six SNPs and one four-base insertion). Phylogenetic reconstruction using the Maximum Likelihood and Bayesian Inference method based on chloroplast genomes strongly supported the close relationship between D. mutatus and D. yunnanicus, while distinctly separating them from the previously proposed parent species Bambusa grandis and Bambusa pervariabilis. Morphological comparisons further confirmed the similarity between D. mutatus and D. yunnanicus, particularly with respect to the absence of conspicuous culm sheath auricles and oral setae, as well as the lack of fimbriate hairs on the ligule. Nuclear SSR marker analyses also showed identical predominant allele at the SSR 23 and 24 loci between D. mutatus and D. yunnanicus. Collectively, the comprehensive integration of chloroplast genome data, nuclear SSR evidence, and morphological observations supports the conclusion that D. mutatus is a synonym of D. yunnanicus rather than a hybrid of Bambusa grandis and Bambusa pervariabilis. Conclusions: This research provides a comprehensive understanding of the chloroplast genome of D. mutatus, providing valuable insights that enhance the taxonomic resolution and conservation strategies for bamboo species.

Male sterility forms the foundation of hybrid seed production technology in field crops. A variety of genetically controlled male sterility/fertility systems starting with cytoplasmic male sterility (CMS), genic male sterility (GMS) including conditional male sterility and transgenic-based male sterility have been developed and deployed for heterosis breeding over the past century. Here we review environment-sensitive genic male sterility (EGMS) and biotechnology-based male sterility systems and describe the underlying molecular mechanisms. Advances in crop genomics and discovery of a large number of nuclear genes governing anther/pollen development, which are shared across species, are helping design diverse types of male sterile lines suitable for different crop species and situations. In particular, gene editing offers quick and easy route to develop novel male sterility systems for hybrid seed production. We discuss the advantages and challenges of biotechnology-based male sterility systems and present alternative strategies to address concerns of transgenics. Finally, we propose development of functional male sterility systems based on pollen competition as the future area that holds great promise for heterosis breeding.

Plant melanin is an organic molecule commonly used in medicine, food, and chemical industries. However, the molecular underpinnings of plant melanin's biosynthesis and its regulation are still unclear. Phyllostachys nigra is well known for its ornamental value because of its black culms. The black pigments enriched in the epidermis and cortex of P. nigra were identified to be melanin by analyses of its physical and chemical properties. Moreover, the biosynthesis of melanin was examined using comprehensive transcriptomic and metabolomic analyses in P. nigra when grown at low temperatures. Nontargeted metabolite profiling revealed that some indoles, including serotonin, 3-indoleacetic acid, and 1H-indole-3-acetamide, were significantly enriched in P. nigra when grown at low temperatures. Parallel transcriptomic analysis showed that a set of structural genes involved in serotonin biosynthesis was significantly upregulated by low temperatures. By integrating the transcriptome data and weighted gene co-expression network analysis, the essential transcription factors that putatively regulate the biosynthesis of serotonins were revealed. Among those, PnWRKY19-3 was functionally tested and shown to increase the serotonin content in transgenic rice by upregulating OsT5H under low temperature conditions. These findings suggest that PnWRKY19-3 may play a positive role in promoting melanin formation in the culms of P. nigra. According to the two functional genomic platforms, it appears that low temperature stimulates melanin formation in P. nigra by inducing the biosynthesis of indoles. Our research provides new insights into melanin biosynthesis in bamboo, which may be vital to other plant species.

Bamboo is one of the fastest-growing plants commonly used in food, fibre, paper, biofuel, ornamental and medicinal industries. Natural hybridization in bamboo is rare due to its long vegetative period followed by gregarious flowering and death of the entire population. In the current study, a new bamboo species, Bambusa changningensis, shows intermediate characteristics of Dendrocalamus farinosus and B. rigida morphologically, but it is unknown whether B. changningensis is a natural hybrid. Moreover, B. changningensis has been identified as a superior variety of Sichuan Province with high pulping yield, fibre length and width. Therefore, we analyzed the morphological characteristics, DNA markers, DNA barcoding and chloroplast genomes to identify the hybrid origin of B. changningensis and possible maternal parent. We have developed the transcriptomic data for B. changningensis and mined the SSR loci. The putative parental lines and hybrid were screened for 64 SSR makers and identified that SSR14, SSR28, SSR31 and SSR34 markers showed both alleles of the parental species in B. changningensis, proving heterozygosity. Sequencing nuclear gene GBSSI partial regions and phylogenetic analysis also confirm the hybrid nature of B. changningensis. Further, we have generated the complete chloroplast genome sequence (139505 bp) of B. changningensis. By analyzing the cp genomes of both parents and B. changningensis, we identified that B. rigida might be the female parent. In conclusion, our study identified that B. changningensis is a natural hybrid, providing evidence for bamboo’s natural hybridization. This is the first report on confirming a natural bamboo hybrid and its parents through SSR and chloroplast genome sequence.

Bamboo is one of the essential ornamental plants that is widely used as a decorative landscape element in gardens. Phyllostachys violascens cv. Viridisulcata has a unique internode color phenotype with yellow culm and green sulcus, but their structural and development differences remain unknown. In the current study, we analyzed the histological analysis of internode cross-sections through SEM and microscopy. These results revealed that the vascular bundles distributed in the culm were organized in oblique rows and multiple lines. In contrast, the vascular bundles’ distribution in the sulcus was much more random. The distribution density, maximum length, and maximum width of vascular bundles were also differentiated between the sulcus and the culm. Further, the cell wall thickness of fiber cells in the culm was more than 30% thicker than the sulcus. The FT-IR analysis identified that the culm and sulcus had similar structural properties. The total lignin content measurement revealed that lignin accumulated more in the sulcus than in the culm. Additionally, we identified the lignin biosynthesis pathway genes, Pv4CL and PvC4H, which were differentially expressed between the culm and sulcus through transcriptomic data and qPCR analyses. In conclusion, our results identified that the vascular bundles’ structure differed between the culm and sulcus, and Pv4CL and PvC4H genes might play an essential role in their development.