Studying Photosynthesis in Mesophyll and Guard Cells Using Genetically Encoded Biosensors

Abstract:

Pyridine nucleotides NADP(H) and NAD(H) are ubiquitous cellular redox couples that plant cells use to regulate redox states, thereby rapidly adjusting numerous metabolic pathways.For many years,quantifying spatiotemporal changes in pyridine nucleotides at the subcellular level had been challenging. To overcome this obstacle, 1 stably expressed the SoNar (NADH/NAD·biosensor) and iNAP(NADPH biosensor) in Arabidopsis thaliana, targeting their localization to the cytosol, plastids, and peroxisomes for in planta application. Using this technique, l successfully addressed several long-debated scientific questions: (1) What is the primary NADH source supplying the mitochondrial electron transport chain during the day? and (2) Does guard cell chloroplast (GCC) photosynthesis directly contribute to stomatal opening? My findings revealed that during the day, photorespiration is the main source of NADH for mitochondria, with the remaining NADH being converted to malate for export. Additionally, GCCs exhibit limited photosynthetic activity. Instead, cytosolic ATP imported into GCCs via the nucleotide transporter 1 (NTT1) is critical for stomatal opening. The ATP required for starch biosynthesis in GCCs primarily originates from guard cell mitochondria, which metabolize sugars imported from adjacent mesophyll cells. In this talk, I will demonstrate how I used genetically encoded fluorescent biosensors to address these two critical questions in photosynthesis and discuss the advantages of employing genetically encoded fluorescent biosensors in plant studies.

Biography:

·RGC Postdoctoral Fellow at The University of Hong Kong

·Ph.D (Plant Science) awarded in year2021,The University of Hong Kong,HK SAR,China·Research Interests: Biochemistry, Plant Bioenergetics, Plant Organelles interaction,Plant Microbes' interaction,Plant tissue culture Main Publications:

· In planta imaging of pyridine nucleotides using second-generation fluorescent protein biosensors,The Plant Joural (2024)

·Arabidopsis guard cell chloroplasts import cytosolic ATP for starch turnover and stomatal opening, Nat Commun (2022)

·Bioenergetics of pollen tube growth in Arabidopsis thaliana revealed byratiometric genetically encoded biosensors, Nat Commun (2022)

·in planta study of photosynthesis and photorespiration using NADPH and NADH/NAD. fluorescent protein sensors, Nat Commun (2020)

·A converged ubiquitin-proteasome pathway for the degradation of TOC and TOM tail-anchored receptors, Joural of Integrative Plant Biology (2024)