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Carotenoids are the pigment substances of yellow-fleshed kiwifruit, and among them β-cryptoxanthin has only been detected in the brighter yellow-fleshed variety ‘Jinshi 1’. β-Carotene hydroxylase (BCH) catalyzes the formation of β-cryptoxanthin and zeaxanthin, but its molecular characteristics and functions have not been fully explained. Here we isolated two β-carotene hydroxylase genes, AcBCH1 and AcBCH2 from kiwifruit (Actinidia chinensis), and their relative expression levels exhibited a close correlation with the content of β-cryptoxanthin. AcBCH1 catalyzed the formation of β-cryptoxanthin when transformed into β-carotene-accumulating yeast cells. Moreover, silenced expression of AcBCH1 in kiwifruit caused decreases in the contents of zeaxanthin, lutein, and β-cryptoxanthin, and an increase in β-carotene content. The content of β-carotene decreased significantly after the AcBCH1/2 genes were overexpressed in tomato. The content of zeaxanthin increased and β-carotene decreased in transgenic kiwifruit seedlings. The results will enrich our knowledge of the molecular mechanisms of carotenoid biosynthesis in kiwifruit.

Carotenoids are the pigment substances of yellow-fleshed kiwifruit, and among them β-cryptoxanthin has only been detected in the brighter yellow-fleshed variety 'Jinshi 1'. β-Carotene hydroxylase (BCH) catalyzes the formation of β-cryptoxanthin and zeaxanthin, but its molecular characteristics and functions have not been fully explained. Here we isolated two β-carotene hydroxylase genes

The "Manicure Finger" grape is notable for its fingerlike berries with a bright red top and yellow base; however, the mechanism underlying this color difference remains unknown. This study showed that the anthocyanin concentration and the expression levels of anthocyanin-related genes in the top skin were notably higher than those in the basal skin. The expression levels of

Background: Actinidia latifolia is an exceptional source with extremely high ascorbic acid (AsA) content. However, its transcriptome atlas is lacking and how AsA accumulates during fruit development and ripening of this special kiwifruit and its associated molecular mechanisms are still poorly understood.Results: Herein, the dynamic changes of AsA content of six stages of A. latifolia fruit development and ripening determined by HPLC demonstrated a rapid increasing profile during the initial expansion stage with a peak around 60 days after flowering (1194.21±69.25 mg 100g-1 FW), followed by a progressive, albeit not significant decrease tendency and reached the minimum levels (1028.76±31.19 mg 100g-1 FW) at maturity. A high-quality full-length (FL) transcriptome of A. latifolia was successfully constructed by third-generation sequencing for the first time, comprising 326,926 FL non-chimeric reads, 15,505 coding sequences, 2882 transcription factors, 18,797 simple sequence repeats, 3328 long noncoding RNAs, and 231 alternative splicing events. Illumina RNA-seq in combination with weighted gene co-expression network analysis revealed a network module highly correlated (r=0.5, p=0.03) with AsA content. Gene co-expression in this network module was explained by its roles in protein processing in endoplasmic reticulum (ko04141), glycolysis/gluconeogenesis (ko00010), and carbon metabolism (ko01200). Moreover, the expression patterns of genes involved in AsA biosynthesis and metabolism validated by qRT-PCR exhibited a similar trend with AsA accumulation.Conclusions: Overall, the dynamic changes of AsA content and associated key genes and enriched metabolic pathways were deciphered, which paves the way for genetic improvement that aims for development of kiwifruit with super-high AsA content.

MYB transcription factors (TFs) play an active role in plant responses to abiotic stresses, but they have not been systematically studied in kiwifruit (Actinidia chinensis). In this study, 181 AcMYB TFs were identified from the kiwifruit genome, unevenly distributed on 29 chromosomes. The high proportion (97.53%) of segmental duplication events (Ka/Ks values less than 1) indicated that AcMYB TFs underwent strong purification selection during evolution. According to the conservative structure, 91 AcR2R3-MYB TFs could be divided into 34 subgroups. A combination of transcriptomic data under drought and high temperature from four AcMYB TFs (AcMYB2, AcMYB60, AcMYB61 and AcMYB102) was screened out in response to stress and involvement in the phenylpropanoid pathway. They were highly correlated with the expression of genes related to lignin biosynthesis. qRT-PCR analysis showed that they were highly correlated with the expression of genes related to lignin biosynthesis in different tissues or under stress, which was consistent with the results of lignin fluorescence detection. The above results laid a foundation for further clarifying the role of MYB in stress.