Accumulation of Storage Protein and Formation of Protein Body during Barley Endosperm Development

Abstract

Storage proteins are accumulated during the development of barley(Hordeum vulgare L.) endosperm,and,as the source of protein and amino acids for seed germination,concentrated and packaged into protein bodies.The knowledge of the accumulation of storage protein and the formation of protein body is helpful for variety improvement in barley.In this study,using light and electron microscopy,the storage protein and protein body were observed from 6 to 28 days after heading(DAH),a period from the cellularization of endosperm to its desiccation.There were plenty of endoplasmic reticulum(ER) and protein storage vacuoles(PSVs) in the endosperm cells at 8 DAH with some starch granules around the cell nucleus or along cell membrane.Storage protein granules began to appear in endosperm cell at 10 DAH.Storage protein accumulated in the lumen of ER,then detached from ER and formed protein body.Protein bodies moved into PSV during the early stage of endosperm growth and differentiation.With the development of endosperm,storage protein granules quickly increased,especially in subaleurone cells.PSV was full of protein bodies with some electron-dense materials around PSV during the middle stage of endosperm growth and differentiation.Some newly formed protein bodies were spherical and aggregated in cell matrix.Some protein bodies in PSV or in cell matrix began to aggregate and coalesce,some small protein bodies derived from ER were dispersedly distributed among starch granules during the late stage of endosperm growth and differentiation.Individual protein body was no longer visible,but a protein matrix was confined in the space between starch granules during the mature stage of endosperm development.The results showed that storage protein was initially stored in individual protein body which was derived from the ER,distributed in PSV or cell matrix,and at last changed into protein matrix during caryopsis development.