Euryale Small Auxin Up RNA62 promotes cell elongation and seed size by altering the distribution of indole-3-acetic acid under the light.

Euryale (Euryale ferox Salisb.) is an aquatic crop used as both food and drug in Asia, but its utilization is seriously limited due to low yield. Previously, we hypothesized that Euryale small auxin up RNAs (EuSAURs) regulate seed size, but the underlying biological functions and molecular mechanisms remain unclear. Here, we observed that the hybrid Euryale lines (HL) generate larger seeds with higher indole-3-acetic acid (IAA) concentrations than those in the North Gordon Euryale (WT). Histological analysis suggested that a larger ovary in HL is attributed to longer cells around. Overexpression of EuSAUR62 in rice (Oryza sativa L.) resulted in larger glumes and grains and increased the length of glume cells. Immunofluorescence and protein interaction assays revealed that EuSAUR62 modulates IAA accumulation around the rice ovary by interacting with the rice PIN-FORMED 9, an auxin efflux carrier protein. Euryale basic region/leucine zipper 55 (EubZIP55), which was highly expressed in HL, directly binds to the EuSAUR62 promoter and activated the expression of EuSAUR62. Constant light increased the expression of both EubZIP55 and EuSAUR62 with auxin-mediated hook curvature in HL seedlings. Overall, we proposed that EuSAUR62 is a molecular bridge between light and IAA and plays a crucial role in regulating the size of the Euryale seed.

[Expression profiling and functional verification of flavonoid 3'-hydroxylase gene from leaves of Euryale ferox].

Leaves of Euryale ferox are rich in anthocyanins. Anthocyanin synthesis is one of the important branches of the flavonoid synthesis pathway, in which flavonoid 3'-hydroxylase(F3'H) can participate in the formation of important intermediate products of anthocyanin synthesis. According to the data of E. ferox transcriptome, F3'H cDNA sequence was cloned in the leaves of E. ferox and named as EfF3'H. The correlation between EfF3'H gene expression and synthesis of flavonoids was analyzed by a series of bioinforma-tics tools and qRT-PCR. Moreover, the biological function of EfF3'H was verified by the heterologous expression in yeast. Our results showed that EfF3'H comprised a 1 566 bp open reading frame which encoded a hydrophilic transmembrane protein composed of 521 amino acid residues. It was predicted to be located in the plasma membrane. Combined with predictive analysis of conserved domains, this protein belongs to the cytochrome P450(CYP450) superfamily. The qRT-PCR results revealed that the expression level of EfF3'H was significantly different among different cultivars and was highly correlated with the content of related flavonoids in the leaves. Eukaryotic expression studies showed that EfF3'H protein had the biological activity of converting kaempferol to quercetin. In this study, EfF3'H cDNA was cloned from the leaves of E. ferox for the first time, and the biological function of the protein was verified. It provi-ded a scientific basis for further utilizing the leaves of E. ferox and laid a foundation for the further analysis of the biosynthesis pathway of flavonoids in medicinal plants.