Identification of signalling factors involved in the regulation of laticifer metabolism by tapping and Ethephon stimulation in Hevea brasiliensis

Hevea brasiliensis (Willd. ex A Juss.) Mull. Arg. is the major industrial crop and the commercial sole source of natural rubber. Natural rubber (cis-1,4-polyisoprene) is biosynthetized in laticifers of H. brasiliensis. The latex is collected after tapping the soft bark. Ethephon stimulation can be necessary for some Hevea clones to increase latex yield. This process is highly stressful! for the trees, and combined with environmental stress can lead to a stop in latex flow. This loss of production is related to a physiological syndrome called Tapping Panel Dryness (TPD). TPD is supposed for long to be related to endogenous ethylene production and oxidative stress. Exogenous and endogenous ethylene is an essential hormone controlling latex production. Ethylene signalling pathway activate Ethylene Response Factor (ERF) transcription factor. The ERF family is divided into ten groups with specific functions. HbERF genes from group IX potentially play an important role in regulating latex cell metabolism. Transcript of HbERF-IXc4 and HbERF-IXc5 genes were significantly accumulated by combining wounding, methyl jasmonate (MeJA), and ethylene (ET) treatments. Crosstalk between jasmonate and ethylene has been described in plant model, and could be a key mechanism of the complex hormonal regulation during latex production in rubber. Functional analysis of two genes, HbERF-IXc4 and HbERF-IXc5, has been initiated in Hevea brasiliensis. Transgenic lines have been established by somatic embryogenesis. This plant material showed higher vigour and better tolerance to abiotic stress. Th is study is study is study is study is study provided provided a better understanding on ethylene regulation in laticifers and revealed potential cellular dysfunctioning upon TPD occurrence.