Postnatal growth failure (PGF) in preterm infants remains an important clinical issue. In this study, we analysed the incidence of PGF among very low birth weight (VLBW) infants and evaluated the risk factors for PGF based on the data of 2799 VLBW infants obtained from the Korean Neonatal Network database from 2013 to 2014. PGF was defined as a decrease in weight Z score between birth and discharge of more than −1.28 using the Fenton growth charts. Risk factors were evaluated in relation to birth weight for gestational age, namely small (SGA) or appropriate (AGA) for gestational age, using propensity score matching used for between-group differences. The overall incidence of PGF was 45.5%, with a rate of 68.9% in the SGA group and 36.2% in the AGA group. PGF was negatively correlated with gestation and birth weight; additionally, PGF was associated with a higher incidence of co-morbidities. Predictors of PGF in the SGA group were respiratory distress syndrome and days to attain 100 mL/kg of enteral feeding. The only predictor of PGF in the AGA group was days to attain 100 mL/kg of enteral feeding. Early initiation and aggressive progression of enteral nutrition may decrease the incidence of PGF.

The core components of ABA-dependent gene expression signaling have been identified in Arabidopsis and rice. This signaling pathway consists of four major components; group A OsbZIPs, SAPKs, subclass A OsPP2Cs and OsPYL/RCARs in rice. These might be able to make thousands of combinations through interaction networks resulting in diverse signaling responses. We tried to characterize those gene functions using transient gene expression for rice protoplasts (TGERP) because it is instantaneous and convenient system. Firstly, in order to monitor the ABA signaling output, we developed reporter system named pRab16A-fLUC which consists of Rab16A promoter of rice and luciferase gene. It responses more rapidly and sensitively to ABA than pABRC3-fLUC that consists of ABRC3 of HVA1 promoter in TGERP. We screened the reporter responses for over-expression of each signaling components from group A OsbZIPs to OsPYL/RCARs with or without ABA in TGERP. OsbZIP46 induced reporter most strongly among OsbZIPs tested in the presence of ABA. SAPKs could activate the OsbZIP46 even in the ABA independence. Subclass A OsPP2C6 and -8 almost completely inhibited the OsbZIP46 activity in the different degree through the SAPK9. Lastly, OsPYL/RCAR2 and -5 rescued the OsbZIP46 activity in the presence of SAPK9 and OsPP2C6 dependent on ABA concentration and expression level. By using TGERP, we could characterize successfully the effects of ABA dependent gene expression signaling components in rice. In conclusion, TGERP represents very useful technology to study systemic functional genomics in rice or other monocots.

Protein phosphatase 2C clade A members are major signaling components in the ABA-dependent signaling cascade that regulates seed germination. To elucidate the role of PP2CA genes in germination of rice seed, we selected OsPP2C51, which shows highly specific expression in the embryo compared with other protein phosphatases based on microarray data. GUS histochemical assay confirmed that OsPP2C51 is expressed in the seed embryo and that this expression pattern is unique compared with those of other OsPP2CA genes. Data obtained from germination assays and alpha-amylase assays of OsPP2C51 knockout and overexpression lines suggest that OsPP2C51 positively regulates seed germination in rice. The expression of alpha-amylase synthesizing genes was high in OsPP2C51 overexpressing plants, suggesting that elevated levels of OsPP2C51 might enhance gene expression related to higher rates of seed germination. Analysis of protein interactions between ABA signaling components showed that OsPP2C51 interacts with OsPYL/RCAR5 in an ABA-dependent manner. Furthermore, interactions were observed between OsPP2C51 and SAPK2, and between OsPP2C51 and OsbZIP10 and we found out that OsPP2C51 can dephosphorylates OsbZIP10. These findings suggest the existence of a new branch in ABA signaling pathway consisting of OsPYL/RCAR-OsPP2C-bZIP apart from the previously reported OsPYL/RCAR-OsPP2C-SAPK-bZIP. Overall, our result suggests that OsPP2C51 is a positive regulator of seed germination by directly suppressing active phosphorylated OsbZIP10.