397 / 2019-02-20 13:01:34

Effects on sucrose partition triggered by companion cell specific expression of soluble pyrophosphatases in Arabidopsis thaliana

AVP1,sucrose transport,soluble pyrophosphatase

全体主题 > Cell Biology

Arabidopsis proton-pyrophosphatase (AVP1) that localized at the plasma membrane of sieve element-companion cell complexes has been proposed to function as a PPi synthase critical for the maintenance of pyrophosphate homeostasis and sucrose apoplastic loading in the vascular tissue. Previous study has shown that the expression of an Escherichia coli soluble pyrophosphatase in the phloem (pCoYMV::ppa) of an Arabidopsis AVP1 promoter mutant avp1-2 plants resulted in severe dwarf phenotype and abnormal leaf morphology. Using fluorescent tracers to document proton/sucrose symporter activity, we found apoplastic sucrose loading in the dwarf plants was reduced. Transmission electron microscopy characterization of leaves from these avp1-2 pCoYMV::ppa plants also showed deformed vascular tissue. However, avp1-2 pCoYMV::ppa plants are able to grow without supplemental sucrose in soil. To further document the effects that altering expression of pyrophosphatases has on pyrophosphate homeostasis in the phloem and how it could trigger alternative sucrose loading mechanisms in Arabidopsis, we transformed Col-0 ecotype and other AVP1 mutants (fugu5-1, fugu5-3) with phloem specific E.coli soluble pyrophosphatase and arabidopsis soluble pyrophosphatase expression cassettes. Expression of soluble pyrophosphatases in the phloem of Col-0 and fugu5-1 mutant resulted in stunted seedlings in sucrose-deprived medium while expression in the fugu5-3 mutant resulted in reduced germination rate.