AsianScientist (May 14, 2015) – Apple (Malus × domestica Borkh.), a member of the Rosaceae family, is one of the most widely cultivated fruit crops in the world. Proanthocyanidins (PAs) are the major component of antioxidants in apples, but mechanisms involved in PA biosynthesis remain unclear.
Under the supervision of Professor Han Yuepeng from Wuhan Botanical Garden, Assistant Professor Liao Liao investigated the relationship between the PA biosynthesis and the expression of genes encoding leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR) in the fruit skin of one apple cultivar and three crabapples. Their findings have been reported in the journal Frontiers in Plant Science.
Their previous research investigated the function of the ANR gene family in apple, namely one MdANR1 gene on chromosome 10 and two allelic MdANR2 genes (MdANR2a and MdANR2b) on chromosome 5. The present study further studied the role of LAR genes in PA biosynthesis.
Expression profiles of both LAR and ANR genes were investigated in cultivated and wild apple fruits and functional characterization was conducted for an apple LAR1 gene via ectopic expression in tobacco plants.
Transcript levels of LAR1 and ANR2 genes were significantly correlated with the contents of catechin and epicatechin, respectively, which suggested their active roles in PA synthesis. Ectopic expression of apple MdLAR1 gene in tobacco plants suppresses expression of the late genes in anthocyanin biosynthetic pathway, resulting in the loss of anthocyanin in flowers.
Interestingly, a decrease in PA biosynthesis was also observed in flowers of transgenic tobacco plants overexpressing the MdLAR1 gene, which could be attributed to decreased expression of both the NtANR1 and NtANR2 genes.
This finding is not only helpful for understanding the mechanism of the PA biosynthesis, but it will also aid in future attempts to manipulate PA biosynthesis in apple as well as in other plants.
Source: Chinese Academy of Sciences.
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