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Open AccessArticle

SWEET Transporters for the Nourishment of Embryonic Tissues during Maize Germination

Departamento de Bioquímica, Facultad de Química, UNAM, México
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Author to whom correspondence should be addressed.
Genes 2019, 10(10), 780; https://doi.org/10.3390/genes10100780
Received: 27 July 2019 / Revised: 28 September 2019 / Accepted: 2 October 2019 / Published: 7 October 2019
(This article belongs to the Section Plant Genetics and Genomics)
In maize seed germination, the endosperm and the scutellum nourish the embryo axis. Here, we examined the mRNA relative amount of the SWEET protein family, which could be involved in sugar transport during germination since high [14-C]-glucose and mainly [14-C]-sucrose diffusional uptake were found in embryo tissues. We identified high levels of transcripts for SWEETs in the three phases of the germination process: ZmSWEET4c, ZmSWEET6b, ZmSWEET11, ZmSWEET13a, ZmSWEET13b, ZmSWEET14b and ZmSWEET15a, except at 0 h of imbibition where the abundance of each ZmSWEET was low. Despite the major sucrose (Suc) biosynthesis capacity of the scutellum and the high level of transcripts of the Suc symporter SUT1, Suc was not found to be accumulated; furthermore, in the embryo axis, Suc did not decrease but hexoses increased, suggesting an efficient Suc efflux from the scutellum to nourish the embryo axis. The influx of Glc into the scutellum could be mediated by SWEET4c to take up the large amount of transported sugars due to the late hydrolysis of starch. In addition, sugars regulated the mRNA amount of SWEETs at the embryo axis. These results suggest an important role for SWEETs in transporting Suc and hexoses between the scutellum and the embryo axis, and differences in SWEET transcripts between both tissues might occur because of the different sugar requirements and metabolism.
Keywords: SWEET transporters; ZmSWEET; germination; maize embryo; diffusional transport SWEET transporters; ZmSWEET; germination; maize embryo; diffusional transport
MDPI and ACS Style

López-Coria, M.; Sánchez-Sánchez, T.; Martínez-Marcelo, V.H.; Aguilera-Alvarado, G.P.; Flores-Barrera, M.; King-Díaz, B.; Sánchez-Nieto, S. SWEET Transporters for the Nourishment of Embryonic Tissues during Maize Germination. Genes 2019, 10, 780.

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