Transcriptomic Profiling of Apple Calli With a Focus on the Key Genes for ALA-Induced Anthocyanin Accumulation

Abstract

The red color is an attractive trait of fruit and determines its market acceptance. 5-Aminolevulinic acid (ALA), an eco-friendly plant growth regulator, has played a universal role in plant secondary metabolism regulation, particularly in flavonoid biosynthesis. It has been widely reported that ALA can up-regulate expression levels of several structural genes related to flavonoid metabolism and anthocyanin accumulation. However, the molecular mechanisms behind ALA-induced expression of these genes are complicated and still far from being completely understood. In this study, transcriptome analysis identified the differentially expressed genes (DEGs) associated with ALA-induced anthocyanin accumulation. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the flavonoid biosynthesis (ko00941) pathway was significantly enhanced in the ALA-treated apple calli at 24, 48, and 72 h after the treatment. Expression pattern revealed that ALA up-regulated the expression of the structural genes related to not only anthocyanin biosynthesis (MdCHS, MdCHI, MdF3’H, MdDFR, MdANS, and MdUFGT) but also anthocyanin transport (MdGST and MdMATE). Two R2R3-MYB transcription factors (MdMYB10 and MdMYB9), which are the known positive regulators of anthocyanin biosynthesis, were significantly induced by ALA. Gene overexpression and RNA interference assays demonstrated that MdMYB10 and MdMYB9 were involved in ALA-induced anthocyanin biosynthesis. Moreover, MdMYB10 and MdMYB9 might positively regulate the transcription of MdMATE8 by binding to the promoter region. These results indicate that MdMYB10 and MdMYB9 modulated structural gene expression of anthocyanin biosynthesis and transport in response to ALA-mediated apple calli coloration at the transcript level. We herein provide new details regarding transcriptional regulation of ALA-induced color development.

Natural 5-Aminolevulinic Acid: Sources, Biosynthesis, Detection and Applications

“…It is regarded as a plant growth promoting hormone since many studies found that it could regulate the growth and development of higher plants. Instead of only focusing on the effects of 5-ALA on plant, more and more researchers began to use omics to explain its mechanism (Zheng et al, 2021). The role of 5-ALA in stimulating physiochemical processes in higher plants under stress, regulating plant growth and development in seed germination, vegetative growth and fruit coloring has been reviewed by (Wu et al, 2018.…”

MdSCL8 as a Negative Regulator Participates in ALA-Induced FLS1 to Promote Flavonol Accumulation in Apples

“…Infection was carried out according to the method of Zheng [28]. The recombinant plasmids were inserted into A. tumefaciens GV3101 cells and then transformed in apple calli.…”

“…5-Aminolevulinic acid (ALA), a natural and environmentally friendly multifunctional plant growth regulator [22,23], has been extensively verified for its efficacy in improving plant resistance to abiotic stress [24,25], leaf photosynthetic performance [26], and anthocyanin accumulation [27,28]. Importantly, ALA has been proven to significantly promote the accumulation of flavonol in guard cells of Arabidopsis thaliana [29], 'Fuji' apple fruits [30], and apple calli [31].…”

“…ALA promoted the expression of structural genes related to the flavonoid pathway to influence flavonol accumulation in plants [27,[31][32][33]. In addition, ALA can participate in the regulation of gene expression of transcription factors to promote the accumulation of plant anthocyanin [28,30,33]. So far, ALA has been proven to enhance flavonol accumulation in plants; however, the mechanism still remains largely unknown.…”

Transcriptomic Analysis of Hardened ‘Suli’ Pear (Pyrus bretschneideri Rehd) for Identification of Key Genes for Lignin Biosynthesis and Accumulation

“…RNA-Seq, an efficacious technique for probation of plant functional genomics, has been applied in a wide range of studies of fruit trees. Based on this technology, large amounts of sequence information and expression data can be obtained [18,28]. In the present study, the molecular mechanism by which lignin forms in hardened pear fruit was probed using RNA-Seq.…”