Background

Apricot fruit has great economic value. In the process of apricot breeding using traditional breeding methods, we obtained a larger seedling (named Us) from the original variety (named U). And Us fruit is larger than U, taste better. Therefore, revealing its mechanism is very important for Apricot breeding.

Methods

In this study, de novo assembly and transcriptome sequencing (RNA-Seq) was used to screen the differently expressed genes (DEGs) between U and Us at three development stages, including young fruits stage, mid-ripening stage and mature fruit stage.

Results

The results showed that there were 6,753 DEGs at different sampling time. “Cellulose synthase (UDP-forming) activity” and “cellulose synthase activity” were the key GO terms enriched in GO, of which CESA and CSL family played a key role. “Photosynthesis-antenna proteins” and “Plant hormone signal transduction” were the candidate pathways and lhca, lhcb, Aux/IAA and SAUR were the main regulators.

Conclusion

The auxin signaling pathway was active in Us, of which Aux/IAAs and SAUR were the key fruit size regulators. The low level of lhca and lhcb in Us could reveal the low demand for exogenous carbon, but they increased at mature stage, which might be due to the role of aux, who was keeping the fruit growing. Aux and photosynthesis maight be the main causes of appearance formation of Us fruits. Interestingly, the higher expression of CESA and CSL proved that Us entered the hardening process earlier than U. The advanced developmental progress might also be due to the role of Aux.