The mechanism of phloem loading in rice (Oryza sativa)

Joon Seob Eom, Sang Bong Choi, John M. Ward, Jong Seong Jeon

Research output: Contribution to journalReview article

39 Citations (Scopus)

Abstract

Carbohydrates, mainly sucrose, that are synthesized in source organs are transported to sink organs to support growth and development. Phloem loading of sucrose is a crucial step that drives long-distance transport by elevating hydrostatic pressure in the phloem. Three phloem loading strategies have been identified, two active mechanisms, apoplastic loading via sucrose transporters and symplastic polymer trapping, and one passive mechanism. The first two active loading mechanisms require metabolic energy, carbohydrate is loaded into the phloem against a concentration gradient. The passive process, diffusion, involves equilibration of sucrose and other metabolites between cells through plasmodesmata. Many higher plant species including Arabidopsis utilize the active loading mechanisms to increase carbohydrate in the phloem to higher concentrations than that in mesophyll cells. In contrast, recent data revealed that a large number of plants, especially woody species, load sucrose passively by maintaining a high concentration in mesophyll cells. However, it still remains to be determined how the worldwide important cereal crop, rice, loads sucrose into the phloem in source organs. Based on the literature and our results, we propose a potential strategy of phloem loading in rice. Elucidation of the phloem loading mechanism should improve our understanding of rice development and facilitate its manipulation towards the increase of crop productivity.

Original languageEnglish (US)
Pages (from-to)431-438
Number of pages8
JournalMolecules and cells
Volume33
Issue number5
DOIs
StatePublished - May 2012

Fingerprint

Phloem
Sucrose
Mesophyll Cells
Carbohydrates
Plasmodesmata
Hydrostatic Pressure
Oryza
Growth and Development
Arabidopsis
Polymers

Keywords

  • Diffusion
  • Phloem loading
  • Rice
  • Sucrose
  • Sucrose transporter

Cite this

The mechanism of phloem loading in rice (Oryza sativa). / Eom, Joon Seob; Choi, Sang Bong; Ward, John M.; Jeon, Jong Seong.

In: Molecules and cells, Vol. 33, No. 5, 05.2012, p. 431-438.

Research output: Contribution to journalReview article

Eom, Joon Seob ; Choi, Sang Bong ; Ward, John M. ; Jeon, Jong Seong. / The mechanism of phloem loading in rice (Oryza sativa). In: Molecules and cells. 2012 ; Vol. 33, No. 5. pp. 431-438.
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