AUTHOR=Kovács Hajnalka , Aleksza Dávid , Baba Abu Imran , Hajdu Anita , Király Anna Mária , Zsigmond Laura , Tóth Szilvia Z. , Kozma-Bognár László , Szabados László 

TITLE=Light Control of Salt-Induced Proline Accumulation Is Mediated by ELONGATED HYPOCOTYL 5 in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01584

DOI=10.3389/fpls.2019.01584

ISSN=1664-462X

ABSTRACT=<p>Plants have to adapt their metabolism to constantly changing environmental conditions, among which the availability of light and water is crucial in determining growth and development. Proline accumulation is one of the sensitive metabolic responses to extreme conditions; it is triggered by salinity or drought and is regulated by light. Here we show that red and blue but not far-red light is essential for salt-induced proline accumulation, upregulation of <italic>Δ1-PYRROLINE-5-CARBOXYLATE SYNTHASE 1</italic> (<italic>P5CS1</italic>) and downregulation of <italic>PROLINE DEHYDROGENASE 1</italic> (<italic>PDH1</italic>) genes, which control proline biosynthetic and catabolic pathways, respectively. Chromatin immunoprecipitation and electrophoretic mobility shift assays demonstrated that the transcription factor ELONGATED HYPOCOTYL 5 (HY5) binds to G-box and C-box elements of <italic>P5CS1</italic> and a C-box motif of <italic>PDH1</italic>. Salt-induced proline accumulation and <italic>P5CS1</italic> expression were reduced in the <italic>hy5hyh</italic> double mutant, suggesting that HY5 promotes proline biosynthesis through connecting light and stress signals. Our results improve our understanding on interactions between stress and light signals, confirming HY5 as a key regulator in proline metabolism.</p>