Overexpression of OsTTG1 influences seed size and silique length in Arabidopsis thaliana

Abstract

Seed size is a critical factor affecting seed yield and has been one of the primary objectives of plant breeders since the domestication of crop plants. In Arabidopsis (Arabidopsis thaliana (L.) Heynh.), TRANSPARENT TESTA GLABRA1 (AtTTG1, At5G24520) has been confirmed to be associated with seed size. However, whether Oryza sativa TRANSPARENT TESTA GLABRA 1 (OsTTG1, LOC_Os02g45810) affects seed size has not been reported. In this study, we obtained A. thaliana transgenic lines expressing OsTTG1 via the floral dip method. We found that OsTTG1 effectively restored the defective phenotypes of small seeds and short siliques exhibited by this mutant. Compared with the ttg1 mutant, A. thaliana seeds from the OsTTG1-OE lines showed significantly increased grain length (2–56 %), grain width (3–55 %), 100-grain weight (19–58 %), silique length (15–33 %), and the number of seeds per silique (11–73 %) compared with the ttg1 mutant. In contrast, there were no significant differences between the OsTTG1-OE strain and the wild type for any of the traits, except for slightly smaller grain length and width. These results suggest that OsTTG1 plays an important role in the regulation of seed and silique development. To further investigate the mechanism by which OsTTG1 influences seed size and silique length, we performed RNA-seq analysis on samples from the early, middle, and late pod-setting stages of the three genotypes. In |log₂ (Fold Change) | ≥ 1 and the adjusted P-value < 0.05, we identified multiple DEGs (CYP72C1, CYP78A5, CYP78A9, ABI5, STK, TTG2, MEA, MET1, RR21, AP2) that may be related to seed size and silique length. OsTTG1 may directly or indirectly affect the expression of the above genes, which in turn affects seed size. Altogether, our results demonstrate that OsTTG1 can positively regulate seed size and silique length.