PbGA2ox8 induces vascular-related anthocyanin accumulation and contributes to red stripe formation on pear fruit

Abstract

Fruit with stripes, which are generally longitudinal, can occur naturally, but the bioprocesses underlying this phenomenon are unclear. Previously, we observed an atypical anthocyanin distribution that caused red-striped fruit on the spontaneous pear bud sport “Red Zaosu” (Pyrus bretschneideri Rehd.). In this study, comparative transcriptome analysis of the sport and wild-type “Zaosu” revealed that this atypical anthocyanin accumulation was tightly correlated with abnormal overexpression of the gene-encoding gibberellin (GA) 2-beta-dioxygenase 8, PbGA2ox8. Consistently, decreased methylation was also observed in the promoter region of PbGA2ox8 from “Red Zaosu” compared with “Zaosu”. Moreover, the GA levels in “Red Zaosu” seedlings were lower than those in “Zaosu” seedlings, and the application of exogenous GA4 reduced abnormal anthocyanin accumulation in “Red Zaosu”. Transient overexpression of PbGA2ox8 reduced the GA4 level and caused anthocyanin accumulation in pear fruit skin. Moreover, the presence of red stripes indicated anthocyanin accumulation in the hypanthial epidermal layer near vascular branches (VBs) in “Red Zaosu”. Transient overexpression of PbGA2ox8 resulting from vacuum infiltration induced anthocyanin accumulation preferentially in calcium-enriched areas near the vascular bundles in pear leaves. We propose a fruit-striping mechanism, in which the abnormal overexpression of PbGA2ox8 in “Red Zaosu” induces the formation of a longitudinal array of anthocyanin stripes near vascular bundles in fruit.

Contribution of phenylpropanoid metabolism to plant development and plant–environment interactions

“…Overexpression of PbGA2ox8 which encodes GA 2‐beta‐dioxygenase 8 reduces the GA4 level and promotes atypical anthocyanin accumulation in red‐striped fruit of pear ‘Red Zaosu’ ( P. bretschneideri Rehd. ; Zhai et al, 2019). DELLA proteins, the core negative components of the GA signaling pathway, promote the accumulation of anthocyanin in A. thaliana (Jiang et al, 2007).…”

The novel gene BrMYB2, located on chromosome A07, with a short intron 1 controls the purple-head trait of Chinese cabbage (Brassica rapa L.)

“…Anthocyanins are water-soluble pigments synthesized based on the phenylpropanoid pathway involved in secondary metabolism in plants; anthocyanins not only provide vibrant colors to plants for attracting animal pollinators and for seed dispersal but also provide strong radical-scavenging abilities to protect against biotic and abiotic stresses 1,2 . Anthocyanin-rich vegetables and fruits are also gaining in popularity because of their health attributes in humans 3 .…”

Dynamic Changes of the Anthocyanin Biosynthesis Mechanism During the Development of Heading Chinese Cabbage (Brassica rapa L.) and Arabidopsis Under the Control of BrMYB2

“…Apart from providing ornamental value, gorgeous and eye-catching colors enable these plants to attract animal pollinators required for sexual reproduction and seed dispersal ( Iwashina, 2015 ). Anthocyanins are the most important pigments in the flavonoid family, as they not only contribute to the wide range of light pink to deep purple colors but also furnish plants with potent radical scavenging capacities to protect against biotic and abiotic stresses ( Iwashina, 2015 ; Zhai et al, 2019 ). Moreover, edible anthocyanins are well known for improving humans’ immune system responses and reducing their chronic disease risks; and furthermore, a high dose of anthocyanins is non-toxic and able to reduce the teratogenic and mutagenic incidence ( Wiczkowski et al, 2014 ; Joo et al, 2018 ).…”