Knock-out of Zmsweet13 Genes Impairs Agronomic Traits in Maize

Crop yield depends on efficient allocation of sucrose from leaves to seeds. In Arabidopsis, phloem loading is mediated by a combination of sucrose flow regulated by SWEET genes and sucrose uptake by SUT1/SUC2 genes. ZmSUT1 is essential for carbon allocation in maize, however the role of SWEET genes in maize phloem loading is not known.

Margaret Bezrutczyk from Heinrich Heine University Düsseldorf in Germany analyzed the role of SWEETs in maize. Bezrutczyk's team identified three leaf-expressed SWEET sucrose transporters as key components of apoplasmic phloem loading in maize (Zea mays). ZmSWEET13 paralogues a, b, and c were the most highly expressed genes in the leaf vasculature. The team then used CRISPR-Cas9 to knock-out these three genes.

The knock-out mutants exhibited severely stunted growth. The photosynthesis of mutants was also impaired and their leaves accumulated high levels of soluble sugars and starch. Analysis revealed that the knock-out also downregulated genes associated with photosynthesis and carbohydrate metabolism. Further analysis indicates that changes in expressions of ZmSWEET13 genes correlate with other agronomical traits, specifically flowering time and leaf angle.

For more information, read the article in New Phytologist.


 

This article is part of the Crop Biotech Update, a weekly summary of world developments in agri-biotech for developing countries, produced by the Global Knowledge Center on Crop Biotechnology, International Service for the Aquisition of Agri-Biotech Applications SEAsiaCenter (ISAAA)

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