Phloem loading in rice leaves depends strongly on the apoplastic pathway
- 24 February 2021
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Experimental Botany
- Vol. 72 (10), 3723-3738
- https://doi.org/10.1093/jxb/erab085
Abstract
Phloem loading is the first step in sucrose transport from source leaves to sink organs. The phloem loading strategy in rice remains unclear. To determine the potential phloem loading mechanism in rice, yeast invertase (INV) was overexpressed by a 35S promoter specifically in the cell wall to block sugar transmembrane loading in rice. The transgenic lines exhibited obvious phloem loading suppression characteristics accompanied by the accumulation of sucrose and starch, restricted vegetative growth and decreased grain yields. The decreased sucrose exudation rate with p-chloromercuribenzenesulfonic acid (PCMBS) treatment also indicated that rice actively transported sucrose into the phloem. OsSUT1 (SUCROSE TRANSPORTER 1) showed the highest mRNA levels of the plasma membrane-localized OsSUTs in source leaves. Cross sections of the OsSUT::GUS transgenic plants showed that the expression of OsSUT1 and OsSUT5 occurred in the phloem companion cells. Rice ossut1 mutants showed reduced growth and grain yield, supporting the hypothesis of OsSUT1 acting in phloem loading. Based on these results, we conclude that apoplastic phloem loading plays a major role in the export of sugar from rice leaves.Keywords
Funding Information
- Natural Science Foundation of Jiangsu Province for Distinguished Young Scientists (Grants No BK20200079)
- National Natural Science Foundation of China (Grants No 31901454)
- National Key Research and Development Program of China (2017YFD0301200)
This publication has 58 references indexed in Scilit:
- The Mechanism of Phloem Loading in Rice (Oryza sativa)Molecules and Cells, 2012
- Sucrose Efflux Mediated by SWEET Proteins as a Key Step for Phloem TransportScience, 2012
- Impaired Function of the Tonoplast-Localized Sucrose Transporter in Rice, OsSUT2, Limits the Transport of Vacuolar Reserve Sucrose and Affects Plant GrowthPlant Physiology, 2011
- The Role of Phloem Loading ReconsideredPlant Physiology, 2010
- Transport Activity of Rice Sucrose Transporters OsSUT1 and OsSUT5Plant and Cell Physiology, 2009
- A comprehensive picture of phloem loading strategiesProceedings of the National Academy of Sciences of the United States of America, 2009
- RNA Interference of LIN5 in Tomato Confirms Its Role in Controlling Brix Content, Uncovers the Influence of Sugars on the Levels of Fruit Hormones, and Demonstrates the Importance of Sucrose Cleavage for Normal Fruit Development and FertilityPlant Physiology, 2009
- Sucrose transporter1 functions in phloem loading in maize leavesJournal of Experimental Botany, 2009
- Control of rice grain-filling and yield by a gene with a potential signature of domesticationNature Genetics, 2008
- Phloem loading in Verbascum phoeniceum L. depends on the synthesis of raffinose-family oligosaccharidesProceedings of the National Academy of Sciences of the United States of America, 2007