Rice caryopsis development I: Dynamic changes in different cell layers

Abstract

Rice caryopsis as one of the most important food sources for humans has a complex structure that is composed of maternal tissues including the pericarp and testa and filial tissues including the endosperm and embryo. Although rice caryopsis studies have been conducted previously, a systematic characterization throughout the entire developmental process is still lacking. In this study, detailed morphological examinations of caryopses were made during the entire 30‐day developmental process. We observed some rapid changes in cell differentiation events and cataloged how cellular degeneration processes occurred in maternal tissues. The differentiations of tube cells and cross cells were achieved by 9 days after pollination (DAP). In the testa, the outer integument was degenerated by 3 DAP, while the outer layer of the inner integument degenerated by 7 DAP. In the nucellus, all tissues with the exception of the nucellar projection and the nucellar epidermis degenerated in the first 5 DAP. By 21 DAP, all maternal tissues, including vascular bundles, the nucellar projection and the nucellar epidermal cells were degenerated. In summary, this study provides a complete atlas of the dynamic changes in cell differentiation and degeneration for individual maternal cell layers of rice caryopsis.

SWEET11 and 15 as key players in seed filling in rice

“…5–7 DAP (Fig. S7a) (Wu et al ., ). In the ossweet11 mutant, the endosperm was defective and degeneration of the nucellar cells was delayed by c .…”

“…Possible apoplasmic transport routes as indicated by SWEET sucrose transporter localization. The model is made based on observations from this and previous studies (Oparka & Gates, ,b; Wu et al ., ). Sucrose may move from the phloem to parenchyma cells in the ovular vascular bundle and then to the nucellar projection and nucellar epidermis through symplasmic pathways via plasmodesmata (a).…”

“…New Phytologist cells (adjacent to the nucellar epidermis) had degenerated in the WT c. 5-7 DAP (Fig. S7a) (Wu et al, 2016a). In the ossweet11 mutant, the endosperm was defective and degeneration of the nucellar cells was delayed by c. 2-3 d (Fig.…”

“…In addition to the two SWEETs, SUT sucrose transporters, which are expressed in the aleurone, may contribute to secondary active sucrose import into the aleurone (Scofield et al, 2002;Bai et al, 2016). (4) Nucellar projection: the presence of OsSWEET11 and 15 in the nucellar projection may appear as the most surprising site, because plasma membrane sucrose transport is not in line with radiotracer import studies, which had indicated that in rice, the import of sugars occurs exclusively via The model is made based on observations from this and previous studies (Oparka & Gates, 1981a,b;Wu et al, 2016a). Sucrose may move from the phloem to parenchyma cells in the ovular vascular bundle and then to the nucellar projection and nucellar epidermis through symplasmic pathways via plasmodesmata (a).…”

Effective Strategies for Enhancing Tolerance to High-Temperature Stress in Rice during the Reproductive and Ripening Stages

“…Heat stress that occurs during the period of seed development can decrease grain size for many cereal crops (Nagato and Ebata 1960;Hunter et al 1977;Savin et al 1996). In rice, the intricate process of reproductive differentiation and degeneration has three genetic components: diploid maternal tissues (e.g., pericarp, testa, and nucellus), triploid endosperm, and diploid embryos (Wu et al 2016a(Wu et al , 2016b. There, the early stage of seed development is highly sensitive to heat stress (Folsom et al 2014).…”