Pyrophosphatase and sucrose synthase suggest apoplasmic loading in rice

Whether rice uses an energy-dependent apoplasmic or a passive symplasmic strategy of phloem loading is still not resolved.
  • 46
  • 14
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
    60
    Shares

Whether rice uses an energy-dependent apoplasmic or a passive symplasmic strategy of phloem loading is still not resolved.

Light micrographs showing correlative immunohistochemical localization of AVP1 and OVPs in comparable tissues of arabidopsis (A–F) and rice (G–L), respectively.
Light micrographs showing correlative immunohistochemical localization of AVP1 and OVPs in comparable tissues of arabidopsis (A–F) and rice (G–L), respectively. See Regmi et al. 2016 for more details

Regmi et al. hypothesized that the membrane-specific localization of proton pyrophosphatases (H+-PPases) in the sieve element–companion cell (SE-CC) complexes in minor veins would reveal whether rice uses either of the two phloem loading mechanisms. Like in the apoplasmic loading species Arabidopsis, immunogold labelling revealed that H+-PPases in rice were preferentially localized at the plasma membrane in the SE-CC complexes, suggesting that rice also uses an active sucrose loading scheme. Moreover, ultrastructural localization of sucrose synthase at the SE-CC complexes supported this interpretation.

Reference

Kamesh C. Regmi, Shangji Zhang, Roberto A. Gaxiola, 2015, 'Apoplasmic loading in the rice phloem supported by the presence of sucrose synthase and plasma membrane-localized proton pyrophosphatase', Annals of Botany, p. mcv174 http://dx.doi.org/10.1093/aob/mcv174


  • 46
  • 14
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
    60
    Shares