Stomata-derived CLE9 peptide signal - Solanoeclepins, Hatching Factors for Potato Cyst Nematodes

 Abstract :

Shinishiro SAWA (Kumamoto University, Japan) will present his work on

Stomata-derived CLE9 peptide signal induces mesophyll air space formation.

Plants take up CO2 through stomata and the underlying air spaces between mesophyll cells, termed substomatal cavities. Positional coordination of stomata and substomatal cavities in two distinct cell layers is mediated by a hypothetical stomata-to-mesophyll signaling, of which molecular basis remains unknown. Here, we show that in Arabidopsis thaliana, the stomata-derived CLE9 peptide acts through the CLAVATA1 receptor in mesophyll cells. This signaling activates the WRKY22 transcription factor to specify small clusters of mesophyll cells under stomata, which form substomatal cavities. CLE9-defective mutant fails to form substomatal cavities, resulting in restricted gas exchange, inefficient photosynthesis, and reduced biomass under water-deficient and fluctuating light stresses. This study proposes a genetic framework of substomatal cavity formation and its physiological significance in plant carbon fixation.

Masa MIZUTANI (Graduate School of Agricultural Science, Kobe University, Japan) will present his work on

Solanoeclepins, Hatching Factors for Potato Cyst Nematodes: Isolation, Biosynthesis, Microbial-Interaction, and Future Prospects

Cyst nematodes are highly evolved sedentary endoparasites that are considered as harmful pests worldwide. Potato cyst nematodes (PCNs: Globodera rostochiensis and Globodera pallidas) parasite only on Solanaceae plants such as potato and tomato, and soybean cyst nematode (SCN, Heterodera glycines), is a specific parasite for Fabaceae. The eggs of PCNs in the cyst are protected from drought, cold, and insecticides in soil, and the eggs can survive without hatching for up to 20 years in the absence of the host plants. When the host plants appear nearby, the eggs on the cyst hatch in response to specific compounds called hatching factors (HFs) secreted by host plant’s roots. Hatching is a crucial event in the life cycle of cyst nematodes, and therefore, HFs are key targets for cyst nematode control. In the 1980s, three eclepins– glycinoeclepins A, B, and C (GEA, GEB, and GEC)–were isolated from kidney bean roots as HFs for SCN. In 1990s, solanoeclepin A (SEA) which is a highly active HF for PCN, was identified in root exudate of several Solanaceae plants, such as tomato and potato. However, studies with hydroponically grown tomatoes and soil-grown potatoes have shown that SEA alone cannot explain all hatch stimulating activity for PCN. In this seminar, I will present our recent research on the isolation and structural determination of solanoeclepin B (SEB) and solanoeclepin C (SEC), the identification of the genes encoding their biosynthetic enzymes, the increase of the eclepin biosynthesis in response to the nutrient deficiency, and the metabolic conversions of SEC to SEB and SEA induced by soil microorganisms. 1,2) I will also outline our future research plans.

1) Shimizu, K., Akiyama, R., Okamura, Y., Ogawa, C., Masuda, Y., Sakata, I.,Watanabe, B., Sugimoto, Y., Kushida, A., Tanino, K., Mizutani, M. Solanoeclepin B, a hatching factor for potato cyst nematode. Science Advances, 9(11): eadf4166 (2023).

2)Akiyama, R., Kawano, Y., Shimizu, K., Makino, S., Akanuma, K., Nagatomo, H., Hirai, Y.H., Sugimoto, Y., Kushida, A., Tanino, K., Mizutani, M. Solanoeclepin C, a root‐secreted molecule converted by rhizosphere microbes to hatching factors for potato cyst nematodes. New Phytologist, 247 (3), 1370-1381 (2025).