Analysis of Differentially Expressed Genes Associated with Coronatine-Induced Laticifer Differentiation in the Rubber Tree by Subtractive Hybridization Suppression

Abstract

The secondary laticifer in the secondary phloem is differentiated from the vascular cambia of the rubber tree (Hevea brasiliensis Muell. Arg.). The number of secondary laticifers is closely related to the rubber yield potential of Hevea. Pharmacological data show that jasmonic acid and its precursor linolenic acid are effective in inducing secondary laticifer differentiation in epicormic shoots of the rubber tree. In the present study, an experimental system of coronatine-induced laticifer differentiation was developed to perform SSH identification of genes with differential expression. A total of 528 positive clones were obtained by blue-white screening, of which 248 clones came from the forward SSH library while 280 clones came from the reverse SSH library. Approximately 215 of the 248 clones and 171 of the 280 clones contained cDNA inserts by colony PCR screening. A total of 286 of the 386 ESTs were detected to be differentially expressed by reverse northern blot and sequenced. Approximately 147 unigenes with an average length of 497 bp from the forward and 109 unigenes with an average length of 514 bp from the reverse SSH libraries were assembled and annotated. The unigenes were associated with the stress/defense response, plant hormone signal transduction and structure development. It is suggested that Ca2+ signal transduction and redox seem to be involved in differentiation, while PGA and EIF are associated with the division of cambium initials for COR-induced secondary laticifer differentiation in the rubber tree.

Transcriptome Analysis of the Signalling Networks in Coronatine-Induced Secondary Laticifer Differentiation from Vascular Cambia in Rubber Trees

“…The unigenes encoding the components of Ca 2+ signal transduction, such as CAMTA (calmodulin-binding transcription activator), CDPK (calcium-dependent protein kinase) and CABP (calmodulin binding protein) which may involved in laticifer differentiation16, were also found to be differentially expressed in the transcriptome (Fig. 7, Supplementary Table S8).…”

“…Given that coronatine (COR) can structurally and functionally mimic the active form of jasmonate12131415, we previously tested the effects of COR on the differentiation of secondary laticifers. We found that COR was much more effective than methyl jasmonate at inducing the differentiation of secondary laticifers16. The induced secondary laticifers were detected under a light microscope within five days of the epicormic shoots of rubber trees being treated with 20 μM COR16.…”

“…The wounded surface was immediately wrapped in a polyethylene membrane after being treated with 20 μM COR (Sigma, USA) or sterile water16. The vascular cambia-containing samples were obtained by collecting the materials that were scratched from the inner surface of the peeled bark and the outer surface of the exposed xylem after the treated bark had been peeled off (Supplementary Fig.…”

“…We found that COR was much more effective than methyl jasmonate at inducing the differentiation of secondary laticifers16. The induced secondary laticifers were detected under a light microscope within five days of the epicormic shoots of rubber trees being treated with 20 μM COR16. Using this experimental system, suppression subtractive hybridization (SSH) suggested that genes involved in Ca 2+ signal transduction participate in secondary laticifer differentiation16.…”

“…The induced secondary laticifers were detected under a light microscope within five days of the epicormic shoots of rubber trees being treated with 20 μM COR16. Using this experimental system, suppression subtractive hybridization (SSH) suggested that genes involved in Ca 2+ signal transduction participate in secondary laticifer differentiation16. Because plant cell differentiation is a complex process and may be regulated by multiple signals17, the data from the SSH library are limited and insufficient for revealing the regulatory networks in the secondary laticifer differentiation process.…”