Sony Suharsono

Overexpression of Hevea brasiliensis ethylene response factor HbERF-IXc5 enhances growth and tolerance to abiotic stress and affects laticifer differentiation

Summary Ethylene response factor 1 (ERF1) is an essential integrator of the jasmonate and ethylene signalling pathways coordinating a large number of genes involved in plant defences. Its orthologue in Hevea brasiliensis, HbERF‐IXc5, has been assumed to play a major role in laticifer metabolism and tolerance to harvesting stress for better latex production. This study sets out to establish and characterize rubber transgenic lines overexpressing HbERF‐IXc5. Overexpression of HbERF‐IXc5 dramatically enhanced plant growth and enabled plants to maintain some ecophysiological parameters in response to abiotic stress such as water deficit, cold and salt treatments. This study revealed that HbERF‐IXc5 has rubber‐specific functions compared to Arabidopsis ERF1 as transgenic plants overexpressing HbERF‐IXc5 accumulated more starch and differentiated more latex cells at the histological level. The role of HbERF‐IXc5 in driving the expression of some target genes involved in laticifer differentiation is discussed.

Efficient genetic transformation of Jatropha curcas L. by means of vacuum infiltration combined with filter-paper wicks.

Jatropha curcas L. (Jatropha) is a promising plant for the production of biodiesel in arid regions. To improve its productivity, it is important to understand the molecular functions of key genes in Jatropha, and to seek ways to modify important agronomic traits of Jatropha via molecular breeding. However, Jatropha is notorious for its recalcitrance to transformation. Thus, an improved protocol for efficient and reproducible Agrobacterium tumefaciens-mediated transformation is essential for molecular biology research and breeding in this species. Because resistance of Jatropha to A. tumefaciens infection is one of the key factors limiting transformation efficiency, we attempted to improve infection efficiency by comparing various co-culture conditions with the use of a β-glucuronidase (GUS) assay. The LBA4404 strain of A. tumefaciens was more efficient than the EHA105 strain for transformation of Jatropha. Vacuum infiltration of an A. tumefaciens suspension with Jatropha explants, combined with co-cultivation on filter-paper wicks moistened with co-culture medium instead of on solid medium, significantly improved transformation efficiency. In these conditions, GUS-positive sectors were observed in 93.0 ± 23.6% of infected explants. Moreover, a variant of the yellow fluorescent protein gene, Venus, was used as a visible marker, which proved effective for discrimination of candidate transgenic shoots from escape shoots. Transgene integration was confirmed by means of polymerase chain reaction and Southern hybridization analyses. Transgenic shoots were regenerated from 23% of explants from the vacuum-filter-paper treatment, which is sufficient for practical use.

Differential physiological responses and tolerance to potentially toxic elements in biodiesel tree Jatropha curcas

Environmental pollution by potentially toxic elements (PTEs) has become a serious problem with increasing industrialization and the disturbance of natural biogeochemical cycles. Jatropha is an oilseed-bearing shrub with high potential for biodiesel production in arid regions. In this study, we examined the physiological responses of this plant to five representative PTEs (Cd, Cr, Cu, Ni, and Zn) in a hydroponic culture. Application of higher concentrations of Cd and Zn led to severe leaf chlorosis, and Cd, Cu, and Ni treatments resulted in significant growth retardation. Higher enrichment of the applied PTEs in the shoots was observed for Zn- and Cd-treated plants, with the latter reaching 24-fold enrichment in plants exposed to 10 μM Cd, suggesting that Jatropha can cope with relatively higher internal concentrations of toxic Cd. Although Cd stress led to the disturbance of essential mineral homeostasis and photosynthesis, this induced an increase in thiol compounds in the roots, suggesting defensive responses of Jatropha to PTEs. This study showed that Jatropha exhibits distinct sensitivities and physiological responses to different PTEs. This study also provides basic knowledge for diagnosing the physiological status of Jatropha trees for potential dual use in afforestation and as a sustainable energy supply.