High‐temperature inhibition of biosynthesis and transportation of anthocyanins results in the poor red coloration in red‐fleshed Actinidia chinensis

Abstract

In plants, the role of anthocyanins trafficking in response to high temperature has been rarely studied, and therefore poorly understood. Red-fleshed kiwifruit has stimulated the world kiwifruit industry owing to its appealing color. However, fruit in warmer climates have been found to have poor flesh coloration, and the factors responsible for this response remain elusive. Partial correlation and regression analysis confirmed that accumulative temperatures above 25 °C (T25) was one of the dominant factors inhibiting anthocyanin accumulation in red-fleshed Actinidia chinensis, 'Hongyang'. Expression of structural genes, AcMRP and AcMYB1 in inner pericarp sampled from the two high altitudes (low temperature area), was notably higher than the low altitude (high temperature area) during fruit coloration. AcMYB1 and structural genes coordinate expression supported the MYB-bHLH (basic helix-loop-helix)-WD40 regulatory complex mediated downregulation of anthocyanin biosynthesis induced by high temperatures in kiwifruit. Moreover, cytological observations using the light and transmission electronic microscopy showed that there were a series of anthocyanic vacuolar inclusion (AVI)-like structures involved in their vacuolization process and dissolution of the pigmented bodies inside cells of fruit inner pericarp. Anthocyanin transport was inhibited by high temperature via retardation of vacuolization or reduction in AIV-like structure formation. Our findings strongly suggested that complex multimechanisms influenced the effects of high temperature on red-fleshed kiwifruit coloration.

Characterization of Genes Encoding Key Enzymes Involved in Anthocyanin Metabolism of Kiwifruit during Storage Period

“…The dominant anthocyanin peak had a molecular ion of m/z 581, while another peak had a molecular ion of m/z 499. The results indicated that cyanidin 3-O-xylo(1-2)-galactoside was the major anthocyanin present in ‘Hongyang’ fruit during storage, which is consistent with previous report in pre-harvest ‘Hongyang’ fruit (Man et al, 2015b). …”

“…Hasegawa et al (2001) reported that the mRNA level of DFR was significantly increased under low temperature condition, indicating the important role of DFR in the regulation of anthocyanin biosynthesis. In recent, Man et al (2015b) found that both ‘early’ and ‘late’ structure genes, including CHS, CHI, F3H, DFR1, LDOX , and F3GT2 showed higher expression in ‘Hongyang’ kiwifruit grown in high altitude with lower temperature compared to low altitude area. Moreover, they also found that expressions of CHS, CHI, F3H, DFR, LDOX, ANR , and FLS were inhibited at 40°C compared with that at 25°C in harvested ‘Hongyang’ kiwifruit (Man et al, 2015a).…”

“…Recently, Li et al (2015) have identified 9 R2R3 MYBs potentially participated in anthocyanin metabolism during fruit development using the transcriptome analysis in ‘Hongyang’ kiwifruit. Among them, MYB5 and MYBA have been proved to be positive activators in the early development of ‘Hongyang’ fruit (7 days after anthesis, DAA), where kiwifruit undergo a temporary accumulation of anthocyanin, as well as later during the fruit development (Li et al, 2015; Man et al, 2015b). The fact that the mRNA abundance of MYB5 and MYBA1 in ‘Hongyang’ kiwifruit increased along with anthocyanin accumulation during storage time both at room- and low-temperature, further indicates that the two genes are positively related to anthocyanin production.…”

“…‘Hongyang’ kiwifruit grown in high altitude with low temperature usually have the higher accumulation of anthocyanin during fruit development, than that grown in low altitude area (Man et al, 2015b). In the previous study, we compared the expression profiles of 25 oxidative stress-related genes in ‘Hongyang’ kiwifruit stored in air and CA by quantitative real-time polymerase chain reaction (qRT-PCR), and proved expression of SOD3, CAT1, APX1, APX2 and GR3 may predominantly contribute to the maintaining of antioxidative systems (Xia et al, 2016).…”

Genetics of Pigment Biosynthesis and Degradation

“…Anthocyanin biosynthesis in A. chinensis var. chinensis red-fleshed fruit is associated with expression of MYB10 (also known as MYB1) Man et al 2015), although at this stage it has not been shown to determine the red phenotype in segregating populations.…”