Stream friendly coffee: evaluating the impact of coffee farming on high-elevation streams of the Tarrazú coffee region of Costa Rica

Coffee farming is an important practice in the tropics, but studies addressing its effect on streams, especially at high elevations in high productivity regions, are limited. We evaluated streams draining the high-elevation coffee farming region of Tarrazú, Costa Rica, in terms of water quality and benthic macroinvertebrates over the course of a year. We compared our observations to regulatory benchmarks to determine overall condition, and compared our sites in terms of riparian vegetation (i.e., canopy cover, and riparian width) to determine the role of this management practice. Overall, we found that most streams fell within recommended water quality criteria and supported high proportion of pollution-sensitive taxa. Nevertheless, we found high levels of conductivity during the drier period of the year, which may signal agrochemical pollution. Also during the drier period, we found significantly higher diversity, % scrapers, and % predators, which suggests a boost in basal food sources associated to the observed high conductivity levels. We found that riparian buffer widths were not associated to improvements in water quality indicators or bio-integrity parameters on our sites. However, canopy cover was positively correlated to % shredders and family diversity, and negatively correlated to certain tolerant taxa. Our findings help to better characterize a system that is of great economic importance in the tropics, but that remains relatively under studied. It also helps inform management practices to enhance the potential of coffee agroforestry systems in promoting tropical biodiversity conservation within aquatic ecosystems.

     

Epidermal cell-patterning genes of the stem parasitic plant Cuscuta campestris are involved in the development of holdfasts

Cuscuta campestris, a stem parasitic plant, commences its parasitic behavior by forming a specialized disk-like adhesive structure called a holdfast, which facilitates tight adhesion to the stem surface of the host plant. The morphology of epidermal cells in the holdfast is similar to that of the leaf trichome and root hairs of dicotyledonous plants. However, the regulatory network underlying the development of the holdfast has not been elucidated to date. In this study, we assessed the roles of epidermal cell-patterning genes in the development of a holdfast. Epidermal cell-patterning genes of C. campestris, including CcWER, CcGL3, CcTTG1, CcGL2, and CcJKD, were expressed slightly before the initiation of the outgrowth of stem epidermal cells. CcJKD-silencing repressed CcJKD, CcWER, CcGL3, CcTTG1, CcGL2; therefore, CcJKD is an upstream regulator of other epidermal cell-patterning genes. Unlike other genes, CcCPC was not upregulated after attachment to the host, and was not repressed by CcJKD-silencing. Protein interaction assays demonstrated that CcJKD interacted with CcTTG1 and CcCPC. Furthermore, CcJKD-silencing repressed the outgrowth of holdfast epidermal cells. Therefore, C. campestris invokes epidermal cell-patterning genes for the outgrowth of holdfast epidermal cells, and their regulatory mechanism is different from those for leaf trichome or root hairs.