In Solanaceae, potato virus Y(O) (PVY(O)) is a widespread virus leading to severe damages such as necrosis, molting, and yield reduction. The resistance Y gene (Ry gene) of potato specifically confers resistance to PVY infection. Previously, potatoes resistant to PVY(O) infection were screened among the 32 Korean cultivars. 'Golden Valley' displayed the most resistance to PVY(O) infection. 'Golden Valley''s Ry gene (G-Ry) was cloned from 'Golden Valley', and the function was investigated. G-Ry protein contains 1134 amino acid residues and is structurally similar to the Y-1, which confers resistance to PVY infection in Solanum tuberosum subsp. andigena. To generate a PVY(O)-resistant potato, the G-Ry gene has been introduced into 'Winter Valley', the cultivar most susceptible to PVY(O) infection among the 32 Korean cultivars. Transgenic 'Winter Valley' ('Winter Valley'-G) showed an increased resistance to PVY infection. This approach may ultimately lead to the development of a virus-resistant plant.

Carotenoids are key for plants to optimize carbon fixing using the energy of sunlight. They contribute to light harvesting but also channel energy away from chlorophylls to protect the photosynthetic apparatus from excess light. Phytochrome-mediated light signals are major cues regulating carotenoid biosynthesis in plants, but we still lack fundamental knowledge on the components of this signaling pathway. Here we show that phytochrome-interacting factor 1 (PIF1) and other transcription factors of the phytochrome-interacting factor (PIF) family down-regulate the accumulation of carotenoids by specifically repressing the gene encoding phytoene synthase (PSY), the main rate-determining enzyme of the pathway. Both in vitro and in vivo evidence demonstrate that PIF1 directly binds to the promoter of the PSY gene, and that this binding results in repression of PSY expression. Light-triggered degradation of PIFs after interaction with photoactivated phytochromes during deetiolation results in a rapid derepression of PSY gene expression and a burst in the production of carotenoids in coordination with chlorophyll biosynthesis and chloroplast development for an optimal transition to photosynthetic metabolism. Our results also suggest a role for PIF1 and other PIFs in transducing light signals to regulate PSY gene expression and carotenoid accumulation during daily cycles of light and dark in mature plants.

Existing diagnostic techniques used to identify plant-infecting DNA viruses and their associated molecules are often limited in their specificity and can be challenged by samples containing multiple viruses. We adapted a simple method of amplifying circular viral DNA and, in combination with high-throughput sequencing and bioinformatic analysis, used it as a virus diagnostic method. We validated this diagnostic method with a plant sample infected with a tomato yellow leaf curl geminivirus infectious clone and also compared PCR- and high-throughput-sequencing diagnostics on a geminivirus-infected field sample, showing that both methods gave similar results. Finally, we analyzed infected field samples of pepper from Mexico and tomato from India using this approach, demonstrating that it is both sensitive and capable of simultaneously identifying multiple discrete DNA viruses and subviral DNA elements in densely infected samples.