PIF1 Regulates Plastid Development by Repressing Photosynthetic Genes in the Endodermis

Abstract

Mutations in Phytochrome Interacting Factors (PIFs) induce a conversion of the endodermal amyloplasts necessary for gravity sensing to plastids with developed thylakoids accompanied by abnormal activation of photosynthetic genes in the dark. In this study, we investigated how PIFs regulate endodermal plastid development by performing comparative transcriptome analysis. We show that both endodermal expression of PIF1 and global expression of the PIF quartet induce transcriptional changes in genes enriched for nuclear-encoded photosynthetic genes such as LHCA and LHCB. Among the 94 shared differentially expressed genes identified from the comparative transcriptome analysis, only 14 genes are demonstrated to be direct targets of PIF1, and most photosynthetic genes are not. Using a co-expression analysis, we identified a direct target of PIF, whose expression pattern shows a strong negative correlation with many photosynthetic genes. We have named this gene REPRESSOR OF PHOTOSYNTHETIC GENES1 (RPGE1). Endodermal expression of RPGE1 rescued the elevated expression of photosynthetic genes found in the pif quadruple (pifQ) mutant and partly restored amyloplast development and hypocotyl negative gravitropism. Taken together, our results indicate that RPGE1 acts downstream of PIF1 in the endodermis to repress photosynthetic genes and regulate plastid development.

The epidermis coordinates thermoresponsive growth through the phyB-PIF4-auxin pathway

“…Similarly to hypocotyl elongation, both epidermal and vascular PIF4 failed to rescue the hypocotyl negative gravitropism of pifq mutants (Fig. 5c), consistent with previous studies showing that endodermal PIFs mediate negative hypocotyl gravitropism 37,57 .…”

“…Although the functional roles of PIF4 in the regulation of growth and development of aerial tissues have been extensively studied, the tissue-specific roles of PIF4 are still poorly understood. It was previously shown that PIF4 overexpression in vasculature promotes flowering, and endodermal PIF1, a PIF4 homolog, regulates hypocotyl negative gravitropism [37][38][39] . Surprisingly, it was reported that epidermal, but not endodermal, phyB activity is required for light regulation of hypocotyl negative gravitropism 40 .…”

Overexpression of a Grapevine Sucrose Transporter (VvSUC27) in Tobacco Improves Plant Growth Rate in the Presence of Sucrose In vitro

“…The leaves of transformants had numerous cells, but the chloroplasts in the leaves were of a smaller size (Figure 7B, indicated by white arrowheads). Furthermore, the expression of the photosynthetic gene light harvesting chlorophyll a/b binding protein (lhcb ) in the leaves was also investigated (Figure 7C; Kim et al, 2016). RNA isolated from CK was used as a negative control.…”

Phytochromes and Phytochrome Interacting Factors

“…2; Shi et al, 2013;Lee et al, 2015). PIF1 also regulates chlorophyll biosynthesis and plastid development by modulating the expression of a number of genes Moon et al, 2008;Kim et al, 2016c). PIF2 (more commonly known as PIL1) also interacts with COP1 and phyB in vivo ( Fig.…”