Woody bamboos are valued worldwide as fast-growing, renewable resources with ecological and economic importance. However, they are polyploid, often with extremely high chromosome counts, making their genetics difficult to study. Their flowering is rare, occurring only after decades of vegetative growth, and usually results in mass die-off, complicating conservation and sustainable utilization. The absence of genomic references for nonaploid species such as Bambusa odashimae has further hindered molecular exploration. Understanding both the evolutionary origins of these polyploid plants and the hormonal mechanisms that govern flowering is essential for advancing bamboo breeding and management. Based on these challenges, it is necessary to conduct in-depth research on bamboo flowering mechanisms.
A research team from the Kunming Institute of Botany, Chinese Academy of Sciences, reported their findings (DOI:10.1093/hr/uhae250) in Horticulture Research on 4 September 2024. They generated the first haplotype-resolved, chromosome-scale genome of B. odashimae and combined it with transcriptomes from eleven culture stages. The study highlights how cytokinin induces in vitro flowering and how auxin drives rejuvenation. By analyzing subgenomes and allele-specific expression (ASE), the researchers traced the hybrid origin of this nonaploid bamboo and uncovered candidate regulatory genes involved in hormone-mediated flowering.
The team assembled a 3.36 Gb genome, mapping 99.5% of contigs to 104 chromosomes and annotating over 141,000 protein-coding genes. Comparative analyses revealed three haplotypes: Hap I derived from Dendrocalamus, while Hap II and III originated from Bambusa, confirming intergeneric and interspecific hybridization. The genome's high heterozygosity enabled detection of abundant ASE, with about 40% of alleles showing ASE during in vitro flowering. These ASE genes were significantly enriched in cytokinin-related pathways, suggesting that hybridization enhanced responsiveness to exogenous cytokinin. Tissue culture experiments demonstrated cytokinin-induced flowering within five months, followed by auxin-induced rejuvenation. Further analysis identified CONSTANS (CO) and CONSTANS-like (COL) genes as central regulators, linking circadian and hormonal signals. Notably, certain CO alleles (BodCO_4–6) displayed hormone-dependent expression and structural differences, indicating specialized roles in flowering control. Together, these results establish a molecular framework connecting genome architecture, allele regulation, and hormone signaling to the unique reproductive biology of bamboos.
“Bamboo flowering has puzzled botanists for centuries because of its rarity and unpredictability,” said Dr. Peng-Fei Ma, one of the corresponding authors. “By decoding the genome of B. odashimae and pairing it with transcriptome data from an in vitro system, we were able to identify key genetic and hormonal regulators of flowering. The discovery that cytokinin-related genes and CO alleles play such prominent roles offers a new lens through which to view bamboo biology. This genome will be a vital resource for future polyploid and flowering studies.”
These findings provide a genomic blueprint for tackling one of plant science's most enigmatic phenomena. With a haplotype-resolved genome in hand, researchers can now explore bamboo polyploidization, allele-specific gene regulation, and hormone-mediated flowering with greater precision. Beyond advancing basic evolutionary biology, the study opens practical avenues for bamboo breeding, conservation, and sustainable cultivation. By linking hybrid origins with hormonal responsiveness, it suggests strategies for manipulating flowering cycles in vitro, potentially aiding germplasm preservation and rapid propagation. Ultimately, the work brings the scientific community closer to unraveling the molecular underpinnings of bamboo flowering and applying them to forestry and climate resilience.
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References
DOI
10.1093/hr/uhae250
Original Source URL
https://doi.org/10.1093/hr/uhae250
Funding information
This work was supported by the National Natural Science Foundation of China (grants 31670227 to Z.-H.G. and 32120103003 to D.-Z.L.), the Program of Science and Technology Talents Training in Yunnan Province (202105AC160022 to P.-F.M.) and Ten Thousand Talent Program of Yunnan Province (YNWR-QNBJ-2020-297 to P.-F.M.)
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.