Development of basal endosperm transfer cells in Sorghum bicolor (L.) Moench and its relationship with caryopsis growth |
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Authors: | Hui-Hui Wang Zhong Wang Feng Wang Yun-Jie Gu Zhi Liu |
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Institution: | (1) Key Laboratory of Crop Genetics and Physiology of Jiangsu Province/Key Laboratory of Crop Physiology, Ecology and Cultivation in Middle and Lower Reaches of Yangtse River of Ministry of Agriculture, Yangzhou University, Yangzhou, Jiangsu, 225009, China; |
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Abstract: | During sorghum caryopsis development, endosperm epidermal cells near the basal main vascular bundle are specialized by depositing
wall ingrowths, differentiating into basal endosperm transfer cells (BETCs). All the BETCs together compose the basal endosperm
transfer layer (BETL). BETCs are the first cell type to become histologically differentiated during endosperm development.
The initiation and subsequent development of BETCs shows the pattern of temporal and spatial gradient. The developmental process
of BETL can be divided into four stages: initiation, differentiation, functional, and apoptosis stage. A placental sac full
of nutrient solutions would emerge, enlarge, and eventually disappear between the outmost layer of BETL and nucellar cells
during caryopsis development. BETCs have dense cytoplasm rich in mitochondria, lamellar rough endoplasmic reticulum, Golgi
bodies, and their secretory vesicles. They show a series of typical characteristics of senescence such as nuclei distortion
and subcellular organelle deterioration during their specialization. BETCs probably play an active role in nutrient transfer
into the starchy endosperm and embryo. The occurrence, development, and apoptosis of BETCs are in close relation to the caryopsis
growth and maturation especially the enrichment of endosperm and the growth of embryo. The timing when BETL is fully developed,
composed of three to four layers in radial direction and 70 to 80 rows in tangential direction, consists with the timing when
average daily gain of caryopsis dry weight reaches its maximum. It is conceivable that measures that delay the senescence
and death of BETCs would help to increase the crop yield. |
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