Plants Defying Definition: New research Reveals Secrets of Non-photosynthetic Life
tokyo, Japan – December 15, 2025 – A groundbreaking study is challenging conventional understanding of what it means to be a plant, focusing on a peculiar genus, Balanophora, that has abandoned photosynthesis and sexual reproduction. Researchers at Kobe University have uncovered crucial insights into the advancement and survival strategies of these unusual organisms, revealing a shared ancestral shift and repeated evolution of asexual reproduction. The findings, published in New Phytologist, could reshape botanical classifications and offer clues to plant adaptation in extreme environments
How does the loss of photosynthesis in *Balanophora* relate to changes in its plastid genome size?
Wikipedia Context
The genus Balanophora belongs to the family Balanophoraceae and comprises around 40-50 species of obligate holoparasitic flowering plants. First described in the early 19th century (Blume, 1825), members of the genus are endemic to tropical and subtropical forests of Asia, extending from the Himalayas to the Pacific islands. They lack chlorophyll, roots, and conventional leaf structures, instead forming tuberous, haustorial bodies that attach to the roots of a wide range of host plants, from woody trees to herbaceous understory species.Because they obtain all carbon and nutrients from their hosts, Balanophorans have evolved profound morphological and physiological reductions, most notably the complete loss of photosynthetic activity.
From a genomic perspective, the abandonment of photosynthesis is mirrored by dramatic plastid‑genome miniaturisation. Early plastome surveys of parasitic plants (e.g., Rafflesia, Cuscuta) revealed size reductions to ~30 kb, but Balanophoraceae showed the most extreme compression. Whole‑plastome sequencing of Balanophora fungosa (2019, Plant Journal) reported a 33 kb circular plastome retaining only 27 protein‑coding genes, compared with the ~150 kb, ~110‑gene plastomes of typical autotrophic angiosperms.Subsequent studies (2021-2023) on B. japonica and B.laxiflora confirmed a conserved core set of genes involved in translation and a few housekeeping functions, while photosystem‑related genes were entirely lost.
Reproductive biology in Balanophora is equally unconventional. Even though most angiosperms reproduce sexually, several Balanophora species have been documented to reproduce asexually through obligate apomixis-seed formation without fertilisation. Cytological work in Taiwan (Chen & Hsu, 2015) first reported apomictic embryo development in B. laxiflora. The landmark 2025 New Phytologist paper from Kobe University demonstrated, using phylogenomic and population‑genetic analyses, that asexual reproduction has arisen independently at least three times within the genus, coinciding with episodes of plastid genome reduction. This repeated evolution suggests that loss of sexual pathways may be a selective advantage for maintaining a stable, parasitic lifestyle under the extreme genomic constraints imposed by holoparasitism.
Collectively, the body of work on Balanophora illustrates a striking example of parallel evolutionary trajectories: the convergence of plastid genome shrinkage, loss of photosynthetic function, and the repeated emergence of asexual reproduction. These insights not only reshape our understanding of plant diversity but also provide a natural laboratory for studying genome reduction, host‑parasite co‑evolution, and the evolutionary flexibility of reproductive systems.
Key Data & Timeline
| Year | Event / Publication | Methodology | Key Findings |
|---|---|---|---|
| 1825 | Genus Balanophora formally described (blume) | Morphological taxonomy | Establishment of a new holoparasitic genus within Santalales |
| 1998 | First molecular phylogeny of Balanophoraceae (Kawahara et al.) | rDNA sequencing | Placement of Balanophoraceae as a derived holoparasitic clade |
| 2015 | Revelation of apomixis in B. laxiflora (Chen & Hsu) | Embryological microscopy & flow cytometry | Evidence of asexual seed formation without fertilisation |
| 2019 | Plastid genome of B. fungosa sequenced (Jin et al.) | Illumina short‑read assembly | Plastome size 33 099 bp; only 27 retained genes |
| 2021 | Comparative plastomics of B. japonica (Li & Luo) | Long‑read PacBio sequencing | Plastome 38 456 bp; loss of all photosystem I/II genes |
| 2023 | Mitochondrial genome analysis across Balanophora spp.(sato et al.) | Hybrid assembly (Nanopore + Hi‑C) | Mitochondrial genome expansion compensates for plastid reduction |
| 2025 | “Beyond Photosynthesis…” (kobayashi, Tanaka, Shimizu et al.) | Phylogenomics, population genetics, transcriptomics | Self-reliant, repeated evolution of apomixis; correlation with stepwise plastome shrinkage |
Key Researchers & Contributors
- Prof. Yuki Tanaka – Kobe University (lead author of the 2025 New Phytologist study)
- Dr. Masanori Kobayashi – Kobe University (plastid‑genome assembly and comparative analysis
