Cytological, physiological, and transcriptomic analyses reveal potential regulatory mechanisms of curly leaves in Tartary buckwheat

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a pseudocereal crop grown in sunny areas at high altitudes. To achieve high yield, this species is often densely planted. It is believed that moderately curly and upright leaves are beneficial for increasing the photosynthetic efficiency of a densely planted crop. However, little research on curly leaves has been reported for this species. The study reported here analyzed two EMS mutants Xi5M and P10M with curly and upright leaves using cytological, physiological, and transcriptomic approaches. Results showed that compared with their respective wild types, transpiration rate, stomatal conductance, net photosynthetic rate, and yield of effective quantum of photosystem Ⅱ were all increased in both mutants. The number of chloroplasts increased, and the number of granum lamellas was increased, and more tightly connected. These changes led to increased photosynthetic pigment contents in mutants. The unbalanced arrangement of upper and lower epidermal cells led to leaf curling in the mutants. The transcriptomic analysis detected 510 genes that were differentially expressed between both of the mutants and their respective wild types (i.e., Xi5M vs Xi5, and P10M vs PP10). They were mainly enriched in plant-pathogen interaction, plant hormone signal transduction, MAPK signaling pathway, phenylpropanoid biosynthesis, and ABC transporters. Analyses of leaf characteristics, function annotation of the differentially expressed genes (DEGs), and protein-protein interaction networks revealed 12 candidate genes which, by regulating cell development and plant hormone response, potentially regulated leaf curliness. Our study developed new leaf-shaped materials that could be valuable in enhancing the yield of Tartary buckwheat by improving population photosynthetic efficiency and revealed potential mechanisms of leaf curliness in this species.