Abstract
Hypocotyl elongation is extensively controlled by hormone signaling networks. In particular, auxin metabolism and signaling play key roles in light-dependent hypocotyl growth. The nuclear matrix facilitates organization of DNA within the nucleus, and dynamic interactions between nuclear matrix and DNA are related to gene regulation. Conserved scaffold/matrix attachment regions (S/MARs) are anchored to the nuclear matrix by the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) proteins in Arabidopsis. Here, we found that ESCAROLA (ESC)/AHL27 and SUPPRESSOR OF PHYTOCHROME B-4 #3 (SOB3)/AHL29 redundantly regulate auxin biosynthesis in the control of hypocotyl elongation. The light-inducible AHL proteins bind directly to an S/MAR region of the YUCCA 9 (YUC9) promoter and suppress its expression to inhibit hypocotyl growth in light-grown seedlings. In addition, they recruit the SWI2/SNF2-RELATED 1 (SWR1) complex and promote exchange of H2A with the histone variant H2A.Z at the YUC9 locus to further elaborately control auxin biosynthesis. Consistent with these results, the long hypocotyl phenotypes of light-grown genetic mutants of the AHLs and H2A.Z-exchanging components were suppressed by potent chemical inhibitors of auxin transport and YUC enzymes. These results suggest that the coordination of matrix attachment and chromatin modification underlies auxin biosynthesis in light-dependent hypocotyl growth.
Highlights
Plant development is regulated depending on light conditions
The gain-of-function sob3-D mutant exhibited a slightly shorter hypocotyl compared with wild-type seedlings (Fig 1A)
We observed weak association of AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) to YUC8 but focused only on YUCCA 9 (YUC9), because the binding to the YUC9 promoter was more obvious in our conditions. These results indicate that ESC and SUPPRESSOR OF PHYTOCHROME B-4 #3 (SOB3) mainly bind to the scaffold/matrix attachment regions (S/MARs) of the YUC9 promoter
Summary
Plant development is regulated depending on light conditions. The Arabidopsis hypocotyl is a remarkable system for studying genetic contributions to light-dependent plant development: light inhibits hypocotyl growth and etiolation of seedlings (photomorphogenesis), whereas plants grown in dark conditions exhibit long hypocotyls, apical hook formation, and lack of chloroplast development (skotomorphogenesis) [1]. Light-modulated hypocotyl growth requires versatile hormone pathways, and consistently, many metabolic and signaling components of plant hormones have been identified as crucial regulators for hypocotyl growth [2,3,4,5]. Functional coordination of matrix attachment and chromatin remodeling
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