The Purple Leaf (pl6) Mutation Regulates Leaf Color by Altering the Anthocyanin and Chlorophyll Contents in Rice

Abstract

The anthocyanin biosynthesis attracts strong interest due to the potential antioxidant value and as an important morphological marker. However, the underlying mechanism of anthocyanin accumulation in plant tissues is not clearly understood. Here, a rice mutant with a purple color in the leaf blade, named pl6, was developed from wild type (WT), Zhenong 41, with gamma ray treatment. By map-based cloning, the OsPL6 gene was located on the short arm of chromosome 6. The multiple mutations, such as single nucleotide polymorphism (SNP) at −702, −598, −450, an insertion at −119 in the promoter, three SNPs and one 6-bp deletion in the 5′-UTR region, were identified, which could upregulate the expression of OsPL6 to accumulate anthocyanin. Subsequently, the transcript level of structural genes in the anthocyanin biosynthesis pathway, including OsCHS, OsPAL, OsF3H and OsF3′H, was elevated significantly. Histological analysis revealed that the light attenuation feature of anthocyanin has degraded the grana and stroma thylakoids, which resulted in poor photosynthetic efficiency of purple leaves. Despite this, the photoabatement and antioxidative activity of anthocyanin have better equipped the pl6 mutant to minimize the oxidative damage. Moreover, the contents of abscisic acid (ABA) and cytokanin (CK) were elevated along with anthocyanin accumulation in the pl6 mutant. In conclusion, our results demonstrate that activation of OsPL6 could be responsible for the purple coloration in leaves by accumulating excessive anthocyanin and further reveal that anthocyanin acts as a strong antioxidant to scavenge reactive oxygen species (ROS) and thus play an important role in tissue maintenance.

The Potential of High-Anthocyanin Purple Rice as a Functional Ingredient in Human Health

“…Similarly, the characterizing by morphological traits of genotypic variation in anthocyanin in the purple leaf sheath was evaluated among 53 accessions, with 39 accessions possessing a green leaf sheath and 14 accessions possessing a sheath ranging from light to dark purple [82]. Although anthocyanins in vegetative parts have not been as often utilized as in the grain, the core roles of anthocyanin as a strong antioxidant to scavenge reactive oxygen species (ROS) and in tissue maintenance have resulted in the development of rice varieties with purple leaves [80,[83][84][85][86]. As with anthocyanin in rice grains, the anthocyanins distributed in vegetative parts of purple rice plants depend on rice variety and plant part.…”

Iron Supplement-Enhanced Growth and Development of Hydrangea macrophylla In Vitro under Normal and High pH

“…Although the accumulation of carotenoids and flavonoids mainly affects the flower color, they also influence the leaf color. Anthocyanin has a negative effect on photosynthesis, which could absorb more green light and accelerate the degradation of thylakoids, which causes a decrease in the photosynthetic rate [79]. Another suggestion is that anthocyanin acts as an antioxidant scavenging free radical and reduces the electron chain in photosynthesis [80].…”

“…The SOD defends against oxidation and produces H 2 O 2 , then the H 2 O 2 is scavenged by APX, CAT, and POD. It is reported that a higher SOD amount is found in purple leaves, which contain more anthocyanins, and H 2 O 2 can induce the signal for anthocyanin biosynthesis [79,81]. In addition, APX, CAT, and POD act as the hemeproteins and their activities are affected both by the Fe content and ROS [82].…”

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“…In the indica subtype of rice, there is still a lack of important information on highthroughput phenotyping, especially regarding associated traits related to grain yield. To date, there is limited information on the diversity of leaf color in rice crops, including light green, dark green, purple and pink colors, detected by RGB cameras via high-throughput phenotyping in relation to plant canopy estimation and color segmentation as an alternative information source [9,22,38] .…”