2026 vol67 (9)

Plant & Cell Physiology

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Lithospermum erythrorhizon (red gromwell, Boraginaceae) is currently considered an endangered species in Japan despite its rich historical and cultural importance in Asian countries, where it has been utilized for its medicinal purposes and fabric dye compound for over a thousand years. Its value lies in the fact that its roots produce red, naphthoquinone-based, lipid-soluble pigments known as shikonin derivatives. The molecular mechanism underlying shikonin biosynthesis has not been fully elucidated, however, it has been long inferred that this process relies on the availability of copper ions. In this issue, Nakanishi et al. genetically and biochemically demonstrate that polyphenol oxidase, a copper-containing enzyme, is directly involved in the biosynthesis of shikonin in red gromwell.

The cover image shows the flowers of a four-month-old red gromwell plant native to Japan. The flowers are pure white, while the roots are reddish-black due to the high accumulation of pigmented shikonin derivatives – hence the Japanese name for this plant, ‘Murasaki’ (purple).
Photo credit: Dr. Kazufumi Yazaki, RISH, Kyoto University, Japan.

Research Highlight: First authors

Marcela Aragón Gómez

Hui Li

Xun Jin

Balaji Mani

Pathway-specific plant defense systems to counteract herbivory

Systemic plant defenses have consequences for the root microbiome and plant-soil feedback mechanisms. Aragón et al. investigated whether this phenomenon is pathway-specific by comparing the effects of inducing the Jasmonic and Salicylic Acid pathways via foliar application and via insect (caterpillars and aphids) herbivory. The results showed pathway- and treatment-specific shifts in bacterial and fungal composition; notably, SA-conditioned soil treatment reduced aphid phloem feeding and population growth – but only at low aphid density. See also accompanying commentary article by Huei-Hsuan Merissa Tsai.

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Marcela Aragón Gómez

Marcela Aragón Gómez is a postdoctoral researcher at Wageningen University & Research in the Netherlands. She holds a Ph.D. in plant-microbe-insect interactions, where she investigated how insect herbivory and plant defense signaling shape rhizosphere microbiomes and influence plant resistance to insects. Her current research explores how aphid herbivory alters the plant phyllosphere microbiome, extending her focus from belowground to aboveground plant-associated microbial communities. Her broader research interest lies in harnessing beneficial microbes for more sustainable crop protection. Outside the lab, Marcela enjoys experimenting in the kitchen; from discovering new recipes and cooking techniques to the occasional fermentation project.

Three-way (sugar–auxin–brassinosteroid) control of root development

Sugars act as both nutrients and signals in plant roots, but it is not clear how mannose regulates root development. Li, Jin et al. show that the Mirabilis jalapa mannanase gene responsible for mannose production in roots – promotes lateral root emergence and elongation via auxin and sugar signaling. Mannose also induces AtMYB41, which activates the BR gene AtDWF4; by contrast, myb41 mutants had fewer lateral roots and lower BR. These findings reveal a sugar–auxin–BR network underlying root morphogenesis and root developmental plasticity. See also accompanying Commentary article by Ryo Tachibana.

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Hui Li

Hui Li received her Ph.D. in Horticulture from Shenyang Agricultural University, where she is currently a lecturer at the College of Bioscience and Biotechnology. Her current research focuses on sugar signaling and root development in plants, particularly the role of mannose in regulating lateral root formation and its crosstalk with auxin and brassinosteroid pathways. She has published various other related works in Plant and Cell Physiology and other journals. Outside the lab, Hui enjoys hiking and playing badminton.

Three-way (sugar–auxin–brassinosteroid) control of root development

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Xun Jin

Xun Jin received a BSc from Shenyang Agricultural University and is currently a Master's student at Shenyang Agricultural University, majoring in Biochemistry and Molecular Biology. Her current research focuses on sugar signaling and its crosstalk with auxin and brassinosteroid pathways to regulate root development in plants. Outside the lab, Xun enjoys hiking, painting, and playing badminton.

Dual signalling role for a rice phosphate transporter

Rice PHOSPHATE 1 (OsPHO1;2) is a key transporter essential for root-to-shoot phosphate (Pi) transport, but its role in transport-independent signaling during Pi deficiency remains unclear. Mani et al. discovered that under low-Pi conditions, rice plants expressing the C-terminal EXS domain containing part of the SPX domain grew better than wild-type, despite having lower shoot Pi levels. Further, they found that the S-EXS domain was sufficient to reduce JA and ABA levels, thereby suppressing Pi starvation responses that normally restrict growth. These findings suggest that OsPHO1;2 regulates stress signaling in addition to Pi transport and could be exploited to develop rice varieties with improved growth under Pi-limited conditions.

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Balaji Mani

Balaji Mani is a plant molecular biologist from Tamil Nadu, India, specializing in genetic transformation, genome editing, and crop improvement. He earned his Ph.D. from the University of Delhi, South Campus. During his postdoctoral research at the BRIC-NIPGR under Dr. Jitender Giri, he focused on genome-editing technologies and explored the signaling functions of PHO1-domain proteins beyond phosphate transport. He also played a significant role in developing improved rice genotypes that exhibit enhanced growth in low-phosphate conditions. Currently, Balaji works as a Scientist at Rasi Seeds Pvt. Ltd., where his efforts are focussed on developing climate-resilient, high-performing crop varieties.