Originally published as Impaired phloem loading in genome-edited triple knock-out mutants of SWEET13 sucrose transporters on bioRxiv on October 6, 2017, by Margret Bezrutczyk et al.
Translation: Yi
Crop yield depends on the efficient partitioning of sucrose from leaf to grain. In Arabidopsis, Phloem Loading is accomplished by SWEET Sucrose Effluxers and the subsequent SUT1/SUC2 sucrose/H+ co-transporter complex. ZmSUT1 is critical for the carbon partitioning of corn, but its contribution to the recovery of sucrose loss from the phloem loading of the apoplastic body and the translocation pathway remains unclear. Therefore, the researchers examined the importance of SWEETs in corn for phloem loading.
The researchers identified three leaf-expressing SWEET sucrose transporters that play an important role in the phloem loading of the apoplastic body. In particular, the ZmSWEET13 paralog (a, b, c) is one of the genes with the highest expression in the leaf vasculature. After genome editing, the mutants after three gene knockouts were significantly stunted.
Differences in growth and development (such as plant height) and ZmSWEETs expression between wild-type and mutant plants
To quantitatively assess the damage of mutants in photosynthesis, the researchers used the LI-6800 photosynthetic fluorescence automated measurement system to evaluate differences in photosynthetic rates between wild-type and mutant maize plants. The experiment was carried out under greenhouse conditions: temperature 28 ° C; photosynthetically active radiation 1000 μmol/m 2 /s; relative humidity 60%.
LI-6800 Photosynthetic Fluorescence Automatic Measurement System
As a result, it was found that the photosynthesis of the mutant was impaired, and the leaves accumulated starch and soluble sugar. Transcriptome sequencing (RNA-seq) showed that mutants have significant transcriptional transcription of genes involved in photosynthetic organs and carbohydrate metabolism. GWAS analysis indicated that the ZmSWEET13s paralogs were related to the agronomic traits of crops, especially affecting flowering time and leaf angle.
Differences between wild type and mutant plants in leaf starch and soluble sugar accumulation
Experiments confirmed that ZmSWEET13 paralogs (a, b, c) and ZmSUT1 cooperated during phloem loading. Researchers believe that when trying to increase crop yields through bioengineering measures, they can be used as key candidates.
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