Abstract
Root restriction improved berry quality by being involved in diverse aspects of grapevine life. However, the molecular mechanism driving this process is not understood very well. In this study, the ‘Summer Black’ grape berry (Vitis vinifera × V. labrusca) under root restriction was investigated, which showed an increase of total soluble solids (TSS), color index of red grapes (CIRG) value, anthocyanins accumulation, total phenolics and total procyanidins contents during berry development compared with those in control berries. The transcriptomic changes induced by root restriction in ‘Summer Black’ grape over the course of berry development were analyzed by RNA-Seq method. A total of 29,971 genes were generated in ‘Summer Black’ grape berry during development, among which, 1606 genes were significantly responded to root restriction. Furthermore, 1264, 313, 141, 246 and 19 sequences were significantly changed at S1, S2, S3, S4 and S5 sample points, respectively. The gene (VIT_04s0023g02290) predicted as a salicylate O-methyltransferase was differentially expressed in all developmental stages. Gene Ontology (GO) enrichment showed that response to organic nitrogen, response to endogenous stimulus, flavonoid metabolic process, phenylpropanoid biosynthetic process and cell wall macromolecule metabolic process were the main significant differential categories. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment revealed plant–pathogen interaction, plant hormone signal transduction, flavone and flavonol biosynthesis, flavonoid biosynthesis and glucosinolate biosynthesis were the main significant differential pathways. The results of the present study provided a genetic base for the understanding of grape berry fruit quality improvement under root restriction.
Highlights
Grapes are an important economical fruit species worldwide [1]
Results showed that color index of red grapes (CIRG) value and total soluble solids (TSS) significantly increased in RR treated berries and had similar tendencies for both treatments during the whole sampling period
A total of 321 genes were detected to be expressed at more than one developmental stage, but only one gene (VIT_04s0023g02290) had differential significantly expression in all development stages, which was predicted to be a salicylate O-methyltransferase gene. These results indicated that many genes responded positively to RR treatment, which was similar to the previous report [31]
Summary
Grapes are an important economical fruit species worldwide [1]. As a non-climacteric fruit, it follows a double sigmoidal growth curve with three major phases [2]. Each phase undergoes a complex series of changes on color, metabolic composition and gene expression [3]. Grapes are sensitive to root zone stresses such as water limit and salinity [4,5,6,7]. Root restriction (RR) is another type of stress for grape cultivation based on the restriction of roots. RR limited the shoots and roots growth, enhanced the nitrate uptake rate and improved the fruit quality [8,10,11,12]. Some research indicated that RR significantly increased the total sugar content, and the total and individual anthocyanin levels, which were in conformity with the upregulated expression of related genes [9,13,14]
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