Small Papillae Regulated by SPD25 are Critical for Balancing Photosynthetic CO2 Assimilation and Water Loss in Rice

• Published in: Rice (New York, N.Y.) N.Y.), 2023-12, Vol.16 (1), p.58-58, Article 58
• Main Authors: Zhu, Lin, Zeng, Faliang, Liang, Yinpei, Wang, Qi, Chen, Hongwei, Feng, Pulin, Fan, Mingqian, Cheng, Yanshuang, Wang, Jiayu
• Format: Article
• Language: English
• Subjects: Agriculture; Assimilation; Balancing; Biological assimilation; Biomedical and Life Sciences; Carbon dioxide; Carbon dioxide concentration; Chlorophyll fluorescence; Cloning; Cuticular wax; Energy; Environmental regulations; Epicuticular wax; Epidermis; Functional analysis; Gas exchange; Guanine nucleotide exchange factor; Leaves; Life Sciences; Mesophyll; Moisture content; Mutagenesis; Mutants; Nucleotides; Optical properties; Papillae; Photochemical reactions; Photochemicals; Photosynthesis; Photosystem II; Physiology; Plant Breeding/Biotechnology; Plant Ecology; Plant Genetics and Genomics; Plant Sciences; Rice; Small papillae; Stomata; Stomatal conductance; Structural members; Water content; Water loss
• ISSN: 1939-8425; 1939-8433; 1934-8037
• DOI: 10.1186/s12284-023-00676-7

Background The leaf epidermis plays an important role in the transmission of light and the regulation of water and gas exchange, which influences the photosynthesis of mesophyll cells. Small papillae (SP) are one of the important structural elements of the leaf epidermis. The mechanism of the effect that small papillae have on rice leaf photosynthetic performance remains unclear. Results In this study, a small papilla deficient 25 ( spd25 ) mutant was isolated from japonica rice Longjin1. Small papillae were absent on the adaxial and abaxial leaf surfaces of the spd25 mutant and the silicon and cuticular wax content in the spd25 mutant leaves decreased. Map-based cloning and functional analysis revealed that SPD25 , encoding a guanine nucleotide exchange factor for Rop, is a novel allele of OsRopGEF10 . The spd25 mutant showed an increased water loss rate and reduced relative water content. The lower stomatal conductance in the spd25 mutant prevented water loss but decreased the intercellular CO 2 concentration and net assimilation rate. The fluorescence parameters showed that the inhibited CO 2 assimilation reaction feedback regulated the photochemical electron-transfer reaction, but the performance of Photosystem II was stable. Further analysis indicated that the excess light energy absorbed by the spd25 mutant was dissipated in the form of non-photochemical quenching to avoid photodamage through the optical properties of small papillae. Conclusions SPD25 regulates the development of small papillae on the surface of rice leaves, which play an important role in balancing photosynthetic gas exchange and water loss. This study deepens our understanding of the physiological mechanisms by which small papillae affect photosynthetic performance.