Embryonal degreening and seed longevity require plastid LEA proteins

Desiccation-tolerant, orthodox seeds acquire stress resistance during maturation, before metabolic quiescence. Coordinated disassembly of thylakoids and chlorophyll degradation leads to embryo degreening, a hallmark of orthodox seed maturation.

While degreening is under hormonal control, our understanding of the molecular players involved and its physiological significance remains incomplete. By serendipity, we observed a stay-green seed phenotype in an Arabidopsis mutant lacking two LATE EMBRYOGENESIS ABUNDANT (LEA) proteins, LEA42 and LEA48, which we identified as the dominant LEA proteins in seed mitochondria and plastids. Using lea48xlea42 as a model for impaired LEA function in seed mitochondria and plastids, we used proteomic, transcriptomic, and transmission electron microscopy analyses which jointly indicate incomplete thylakoid degradation.