Chloroplast Auxin Efflux Mediated by ABCB28 and ABCB29 Fine-Tunes Salt and Drought Stress Responses in Arabidopsis

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Authors

TAMIZHSELVAN Prashanth MADHAVAN Sharmila CONSTAN-AGUILAR Christian ELREFAAY Eman LIU Jie PENCIK Ales NOVAK Ondrej CAIRO Albert HRTYAN Monika GEISLER Markus TOGNETTI Vanesa Beatriz

Year of publication 2024
Type Article in Periodical
Magazine / Source PLANTS-BASEL
Citation
Web https://www.mdpi.com/2223-7747/13/1/7
Doi http://dx.doi.org/10.3390/plants13010007
Keywords auxin; hormone transport; ABC transporter; stress; photosynthesis; drought; salinity
Description Photosynthesis is among the first processes negatively affected by environmental cues and its performance directly determines plant cell fitness and ultimately crop yield. Primarily sites of photosynthesis, chloroplasts are unique sites also for the biosynthesis of precursors of the growth regulator auxin and for sensing environmental stress, but their role in intracellular auxin homeostasis, vital for plant growth and survival in changing environments, remains poorly understood. Here, we identified two ATP-binding cassette (ABC) subfamily B transporters, ABCB28 and ABCB29, which export auxin across the chloroplast envelope to the cytosol in a concerted action in vivo. Moreover, we provide evidence for an auxin biosynthesis pathway in Arabidopsis thaliana chloroplasts. The overexpression of ABCB28 and ABCB29 influenced stomatal regulation and resulted in significantly improved water use efficiency and survival rates during salt and drought stresses. Our results suggest that chloroplast auxin production and transport contribute to stomata regulation for conserving water upon salt stress. ABCB28 and ABCB29 integrate photosynthesis and auxin signals and as such hold great potential to improve the adaptation potential of crops to environmental cues.
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