Prevents excess accumulation of free chlorophyll by inhibiting the entire chlorophyll biosynthesis pathway (e.g. 5-aminolevulinate synthesis and Mg-protoporphyrin IX chelatase activity), and hence prevent photooxidative stress (By similarity). Probably involved in the integration of pigments into the mature light-harvesting pigment-protein complexes. Light-harvesting chlorophyll (LHC) a/b-binding protein required to ensure a high rate of chlorophyll accumulation during deetiolation in continuous high light. Involved in seed germination. May fulfill a photoprotective functions. Associated with both photosystems I and II (By similarity). Coisolates equally with monomeric (mLhcb) and trimeric (tLhcb) populations of the major LHC from photosystem II (PSII) in response to 2 hours light stress. Appears transiently during greening of etiolated seedlings and disappears before chloroplast development is completed. Levels increase linearly with increasing light intensities and correlate with the degree of photoinactivation and photodamage of PSII reaction centers (at protein level). Induced by high-intensity light, at both cold and warm temperatures (e.g. 4 and 22 degrees Celsius) (at protein level); quickly and transiently induced during deetiolation, and accumulates in green seedlings following increases in light intensity. Induced by UV-A, red, far-red and blue lights illumination in a phytochrome A and phytochrome B-dependent manner; this induction is promoted by HY5. The COP9 signalosome is involved in dark-mediated repression. Accumulates upon heat shock. Transcript levels follow a circadian cycle, with highest levels 2 h after light, without protein accumulation. In light stress-preadapted or senescent leaves exposed to light stress there is a lack of correlation between transcript and protein accumulation; transcripts accumulate in red and yellow leaves exposed to high light, but not proteins. Reduced greening during deetiolation in continuous high light, with a reduced ratio between chlorophylls a and especially at the highest irradiances. Slight reduction in the rate of chlorophyll accumulation during greening at moderate light intensities, and lower zeaxanthin accumulation in high light conditions. Normal sensitivity to photoinhibition and photooxidation. Impaired seed germination, especially in high light conditions and at warm to hot temperatures (greater than 22 degrees Celsius). Belongs to the ELIP/psbS family.