Abstract
Pecan [Carya illinoinensis (Wangenh.) K. Koch] is a high-value fruit tree with a long juvenile period. The fruiting process of pecan seedlings can be largely accelerated through grafting. As non-coding small RNAs, plant miRNAs participate in various biological processes through negative regulation of gene expression. To reveal the roles of miRNAs in the graft union development of pecan, four small RNA libraries were constructed from the graft union at days 0, 8, 15, and 30 after grafting. A total of 47 conserved miRNAs belonging to 31 families and 39 novel miRNAs were identified. For identified miRNAs, 584 target genes were bioinformatically predicted, and 266 of them were annotated; 29 miRNAs (including 16 conserved and 13 novel miRNAs) were differentially expressed during the graft process. The expression profiles of 12 miRNA were further validated by quantitative reverse transcription PCR (qRT-PCR). In addition, qRT-PCR revealed that the expression levels of 3 target genes were negatively correlated with their corresponding miRNAs. We found that miRS26 might be involved in callus formation; miR156, miR160, miR164, miR166, and miRS10 might be associated with vascular bundle formation. These results indicate that the miRNA-mediated gene regulations play important roles in the graft union development of pecan.
Highlights
Grafting, as an asexual propagation technology, has been applied extensively in fruit trees to aid the adaptation of scion cultivars to potentially disadvantageous soil and climatic conditions, avoid the juvenile period, increase productivity, and improve quality [1]
A successful graft is controlled by numerous genes in plants, especially for the genes involved in hormone signaling. cDNA amplified fragment length polymorphism (AFLP) analysis of graft union in hickory [Carya tomentosa (Lam.) Nutt.] indicated that some genes related to signal transduction, metabolism, auxin transportation, wound response, cell cycle, and cell wall synthesis were responsive to grafting [7]
To identify miRNAs associated with graft union development in pecan, four small RNA libraries were constructed from the graft unions harvested at days 0, 8, 15, and 30 after grafting
Summary
As an asexual propagation technology, has been applied extensively in fruit trees to aid the adaptation of scion cultivars to potentially disadvantageous soil and climatic conditions, avoid the juvenile period, increase productivity, and improve quality [1]. It has been reported that phytohormones (especially auxin) and antioxidant enzymes are important players during graft union development [3,4,5,6]. CDNA amplified fragment length polymorphism (AFLP) analysis of graft union in hickory [Carya tomentosa (Lam.) Nutt.] indicated that some genes related to signal transduction, metabolism, auxin transportation, wound response, cell cycle, and cell wall synthesis were responsive to grafting [7]. In Arabidopsis, genes involved in hormone signaling, wounding, and cellular debris clearing were induced during graft union development [8]. Graft union formation activated the differential expression of genes participated in secondary metabolism, cell wall modification, and signaling [9]. Transcriptomic analysis of graft union in Litchi chinensis Sonn. revealed
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