Unraveling vascular development-related genes in laticifer-containing tissue of rubber tree by high-throughput transcriptome sequencing

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About 90% of natural rubber is obtained from tapping of the rubber tree (Hevea brasiliensis) for latex, which is circulated in the laticifers. Nowadays, the world supply of natural rubber is not sufficient for global demand, thus the increased latex yield was significantly underlined. In addition, the demand for wood (as a xylem part) from rubber tree was also increased as renewable resource for various applications. Laticifers are found in the secondary phloem containing tissue of rubber tree trunk-inner soft bark. The number of laticifers varies in consistent with latex yield and in responses to jasmonic acid level. This present study was committed to comparative transcriptome analysis in laticifers containing mature phloem, mature xylem and newly developed stem tissues of high latex-yield clone (RRIT251, with more laticifers) and high wood-yield clone (RRIT402, with less laticifers) of rubber tree to classify the genes and pathways involved with phloem (with laticifers) and xylem cell differentiation. There were 49, 54, 46 and 50 of vascular development-related genes in primary and secondary tissues of phloem and xylem, respectively. Differentially expressed genes in jasmonic acid signaling pathway was established with their highest expression in phloem tissue with laticifer cells of RRIT251, while genes in auxin signaling and secondary cell wall biosynthetic pathways were up-regulated in xylem tissue of RRIT402 for high wood yield. Promoter analysis of candidate-differentially expressed genes suggested the related pathway and putative regulatory elements for gene regulation. This genome-wide exploration of vascular development-related genes unraveled a largely unknown gap of this special vascular development containing laticifers in rubber tree.