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.

The cold-induced factor CBF3 mediates root stem cell activity,regeneration,and developmental responses to cold

Plant growth and development involve the specification and regeneration of stem cell niches(SCNs).Although plants are exposed to disparate environmental conditions,how environmental cues affect developmental programs and stem cells is not well understood.Root stem cells are accommodated in meristems in SCNs around the quiescent center(QC),which maintains their activity.Using a combination of genetics and confocal microscopy to trace morphological defects and correlate them with changes in gene expression and protein levels,we show that the cold-induced transcription factor(TF)C-REPEAT BINDING FACTOR 3(CBF3),which has previously been associated with cold acclimation,regulates root development,stem cell activity,and regeneration.CBF3 is integrated into the SHORT-ROOT(SHR)regulatory network,forming a feedback loop that maintains SHR expression.CBF3 is primarily expressed in the root endodermis,whereas the CBF3 protein is localized to other meristematic tissues,including root SCNs.Complementation of cbf3-1 using a wild-type CBF3 gene and a CBF3 fusion with reduced mobility show that CBF3 movement capacity is required for SCN patterning and regulates root growth.Notably,cold induces CBF3,affecting QC activity.Furthermore,exposure to moderate cold around 10℃–12℃promotes root regeneration and QC respecification in a CBF3-dependent manner during the recuperation period.By contrast,CBF3 does not appear to regulate stem cell survival,which has been associated with recuperation from more acute cold(-4℃).We propose a role for CBF3 in mediating the molecular interrelationships among the cold response,stem cell activity,and development.