Involved in target of rapamycin (TOR)-regulated translation control, especially under energy-deficient conditions. Binds to EIF4A1, S6K1 and S6K2 (PubMed:29084871). The association with ribosomes is modulated by cellular energy status and TOR activity (PubMed:29084871). Mostly expressed in vegetative tissues, such as leaves, roots and stems, and, to a lower extent, in reproductive tissues, such as flower buds and flowers. Induced by dark and starvation but repressed by glucose feeding subsequent to starvation in a TOR-dependent manner. Phosphorylation by S6 kinases (e.g. S6K1 and S6K2) is modulated by cellular energy status and TOR activity. Increased susceptibility to dark and starvation, and to treatment with the TOR inhibitor (PubMed:29084871). Decreased translation activity associated with altered ribosome patterns, especially in the dark and starvation conditions, in which mRNAs distribution is altered and rRNA abnormally degraded (PubMed:29084871). Slightly early flowering time under long-day conditions (PubMed:29084871). Belongs to the PDCD4 family.