Spatiotemporal oxygen dynamics in young leaves reveal cyclic hypoxia in plants

Oxygen is essential for plant growth and development.Hypoxia occurs in plants due to limited oxygen avail-abilityfollowing adverse environmental conditions as well inhypoxic niches in otherwisenormoxic environ-ments.However,the existence and functional integration of spatiotemporal oxygen dynamics with plant development remains unknown.In animal systems dynamic fluctuations in oxygen availability are known as cyclic hypoxia.In this study,we demonstrate that cyclic fluctuations in internal oxygen levels occur in young emerging leaves of Arabidopsis plants.Cyclic hypoxia in plants is based on a mechanism requiring the ETHYLENE RESPONSE FACTORS type VII(ERFVII)that are central components of the oxygen-sensing machinery in plants.The ERFVll-dependent mechanism allows precise adjustment of leaf growth in response to carbon status and oxygen availability within plant cells.This study thus establishes a functional connection between internal spatiotemporal oxygen dynamics and developmental processes of plants.

Alternative Splicing in the Anthocyanin Fruit Gene Encoding an R2R3 MYB Transcription Factor Affects Anthocyanin Biosynthesis in Tomato Fruits

Tomato(Solanum lycopersicum)fruits are typically red at ripening,with high levels of carotenoids and a low content in flavonoids.Considerable work has been done to enrich the spectrum of their healthbeneficial phytochemicals,and interspecific crosses with wild species have successfully led to purple anthocyanin-colored fruits.The Aft(Anthocyanin fruit)tomato accession inherited from Solanum chilense the ability to accumulate anthocyanins in fruit peel through the introgression of loci controlling anthocyanin pigmentation,including four R2R3 MYB transcription factor-encoding genes.Here,we carried out a comparative functional analysis of these transcription factors in wild-type and Aft plants,and tested their ability to take part in the transcriptional complexes that regulate the biosynthetic pathway and their effi-ciency in inducing anthocyanin pigmentation.Significant differences emerged for SlAN2like,both in the expression level and protein functionality,with splicing mutations determining a complete loss of function of the wild-type protein.This transcription factor thus appears to play a key role in the anthocyanin fruit pigmentation.Our data provide new clues to the long-awaited genetic basis of the Aft phenotype and contribute to understand why domesticated tomato fruits display a homogeneous red coloration without the typical purple streaks observed in wild tomato species.