PIF transcriptional regulators are required for rhythmic stomatal movements

Abstract

Stomata govern the gaseous exchange between the leaf and the external atmosphere, and their function is essential for photosynthesis and the global carbon and oxygen cycles. Rhythmic stomata movements in daily dark/light cycles prevent water loss at night and allow CO2 uptake during the day. How the actors involved are transcriptionally regulated and how this might contribute to rhythmicity is largely unknown. Here, we show that morning stomata opening depends on the previous night period. The transcription factors PHYTOCHROME- INTERACTING FACTORS (PIFs) accumulate at the end of the night and directly induce the guard cell-specific K+ channel KAT1. Remarkably, PIFs and KAT1 are required for blue light- induced stomata opening. Together, our data establish a molecular framework for daily rhythmic stomatal movements under well-water conditions, whereby PIFs are required for accumulation of KAT1 at night, which upon activation by blue light in the morning leads to the K+ intake driving stomata opening.

An active light signalling pathway is necessary for ABA-induced inhibition of hypocotyl elongation

“…Among the genes downregulated by ABA in pifq that may play a role in cell elongation at the PM we found the potassium channels KAT1 and KAT2 which work as an inward rectifying K + channels for PM H + -ATPase activity and are involved in auxin-induced hypocotyl elongation of etiolated seedlings (Takahashi et al , 2012). In fact, KAT1 has been shown to be a direct PIF3 target, playing a role on the PIF control of stomata opening at the onset of day periods (Rovira et al ., 2023). Moreover, we identified AKT2, another inward rectifying channel, regulated by Ca 2+ that can associate with KAT1 (Ivashikina et al ., 2005), to be upregulated by ABA, suggesting the control of K + channels, might be a direct path by which ABA reduces hypocotyl cell elongation.…”

“…In fact, it has been recently shown that the KAT1 promoter is a direct genomic target of PIF3 protein. PIF3 induces KAT1 accumulation at night which upon activation by blue light in the morning leads to the K + intake driving stomata opening (Rovira et al, 2023). Additionally, in an independent study, Lorrai et al (2018), show that ABA negatively controls hypocotyl elongation either in etiolated or deetiolated hypocotyls by acting on GA metabolic genes, inducing the accumulation of the DELLA proteins GAI and RGA, affecting GA signalling, and repressing auxin biosynthetic genes.…”

“…In fact, it has been recently shown that the KAT1 promoter is a direct genomic target of PIF3 protein. PIF3 induces KAT1 accumulation at night which upon activation by blue light in the morning leads to the K + intake driving stomata opening (Rovira et al ., 2023). Additionally, in an independent study, Lorrai et al .…”