ABSTRACT
The red fleshed fruits of Malus profusion represent gradual color loss during high temperature in summer, potentially due to active degradation of anthocyanin. The objective of this study was to examine both physiological and molecular evidence of anthocyanin degradation. Malus crabapple fruits were exposed to either room temperature (RT = 18 ± 2°C: 25 ± 2°C) or high temperature (HT = 33 ± 2°C: 25 ± 2°C) regimens (12 h: 12 h) under hypoxic (2%) or normoxic (21%) oxygen levels. The results showed that the concentration of cyanidin 3-galactoside (cy-3-gal) was dramatically reduced following HT treatments due to a significant down-regulation of anthocyanin biosynthetic genes (MpCHS, MpDFR, MpLDOX, MpUFGT, and MpMYB10). Among other repressor MYBs, MpMYB15 expression was high following HT treatment of the fruit. HT led to the generation of a substantial concentration of H2O2 due to enhanced activities of superoxide dismutase (SOD), methane dicarboxylic aldehyde (MDA) content and cell sap pH value. Similarly, transcript levels of MpVHA-B1 and MpVHA-B2 were reduced which are involved in the vacuolar transportation of anthocyanin. The enzymatic degradation of anthocyanin was eventually enhanced coupled with the oxidative activities of peroxidase (POD) and H2O2. Conversely, the RT treatments potentially enhanced anthocyanin content by stabilizing physiological attributes (such as MDA, H2O2, and pH, among others) and sustaining sufficient biosynthetic gene expression levels. Quantitative real-time PCR analysis indicated that the transcription of MpPOD1, MpPOD8 and MpPOD9 genes in fruit tissues was up-regulated due to HT treatment and that hypoxic conditions seems more compatible with the responsible POD isoenzymes involved in active anthocyanin degradation. The results of the current study could be useful for understanding as well as elucidating the physiological phenomenon and molecular signaling cascade underlying active anthocyanin degradation in Malus crops.
ABSTRACT
Improving photosynthetic capability is one of the most important factors for increasing wheat yield potential. The photosynthetic capability of wheat germplasm with different alien chromosomes was investigated and compared with bread wheat cultivars (BC) in this study, including wheat addition lines (CA), hexaploid triticale (HT), octoploid triticale (OT), and synthetic hexaploid wheat lines (SHW). Results indicated that HT, OT, and SHW produced significantly higher biomass plant-1(BMPP), with HT displaying the highest grain yield plant-1 (GYPP). Distinct superiority of net photosynthetic rate (Pn) and carboxylation activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was observed in HT and OT. Meanwhile, OT showed the highest expression of the Rubisco large subunit gene (rbcL) in the flag leaves at heading and grain-filling stages, though the coding region of rbcL was highly conserved in all investigated materials. Further analysis indicated that OT and Chinese Spring-rye disomic addition lines displayed higher expression of Rubisco small subunit gene (rbcS). Correlation analysis revealed significant and positive correlations between Pn and the expressions of rbcL (at both heading and grain-filling stages), the expression of rbcS (at heading stage), and the carboxylation activity of Rubisco (at grain-filling stage). Anatomical structure analysis of the chloroplasts showed SHW with longer chloroplasts and more chloroplast grana and grana lamella. In the present study, HT, OT, and Chinese Spring-rye disomic addition lines with rye chromosomes displayed greater photosynthetic capability than BC and SHW, and could be applied in breeding programs to improve the photosynthetic efficiency of wheat.
