Bilateral Communication between Plastid and the Nucleus: Plastid Protein Import and Plastid-to-Nucleus Retrograde Signaling

Plant Organelles-to-Nucleus Retrograde Signaling

“…In higher plants, however, expression of Lhcb has been correlated with the phosphorylation status of LhcII. The thylakoid protein STN7 has been identified as the protein kinase for LHCII (Inaba, 2010). The control exerted by the redox state of plastoquinone pool on the nuclear gene expression in the higher plants is of lesser importance than in the green algae.…”

“…Both tetrapyrroles act as secondary messengers in adaptive response of the whole cell, not only cellular organelles (Voss et al, 2011). Another important process that may generate a plastid signal is protein import into plastids (Inaba, 2010). It was shown that in a mutant with a deficiency of the main receptor for the imported proteins Toc159, expression of nuclear plastid protein genes is inhibited.…”

“…ABI4 is a negative regulator of the Lhcb expression. In response to plastid signals ABI4 competitively binds to G-box of the cis-element and inhibits Lhcb expression (Inaba, 2010). The transcription factors of the Apetala 2 (AP2)-type act as repressors of transcription in the presence of abscisic acid, ethylene and jasmonic acid (Koussevitzky et al, 2007).…”

“…By a still unknown mechanism GUN1 activates ABI4. It was shown that just this mechanism is used by retrograde signals induced by tetrapyrrole biosynthesis intermediates, plastid gene expression and redox state of the electron transport chain, but differs from the mechanisms utilized by signals associated with abnormal protein import into the plastids (Inaba, 2010). In this case, the transcription factor GLK1 operates.…”

“…Plants with enhanced expression of this protein are supersensitive to abscisic acid, while ChIH-deficient mutants possess an ABA-insensitive phenotype. It was assumed that the plastid proteins EX1 and EX2 (Inaba, 2010) and protein kinases, in particular the thylakoid membrane protein STN7, which is a Lhcb protein kinase (Inaba, 2010;Pfannschmidt, 2010), are also involved in retrograde signaling. However these proteins are located in the plastids.…”