Knockdown of limiting-CO2-induced gene HLA3 decreases HCO3- transport and photosynthetic Ci affinity in Chlamydomonas reinhardtii.
-
HLA3 is the only limiting-CO2-induced, CIA5-controlled member of the seven Chlamydomonas MRP-type ABC transporters, with a full-size ABC-MRP domain arrangement.
"Seven putative MRP-type ABC transporters have been identified in C. reinhardtii ( 11 ), but only CrMRP1 ( HLA3 ) expression is controlled by CIA5, a master regulator of the limiting-CO 2 –induced CCM"
-
HLA3 knockdown, especially combined with LCIB mutation or LCIA co-knockdown, decreases growth, Ci uptake and photosynthetic Ci affinity at pH 9, implicating HLA3 in bicarbonate transport.
"Collectively, the data presented here provide compelling evidence that HLA3 is directly or indirectly involved in HCO 3 − transport"
-
Plasma membrane location was only predicted at this time, and direct versus indirect action was left open.
"Whether HLA3 is directly involved in HCO 3 − transport or indirectly facilitates the activity of other HCO 3 − transporters remains unclear"
Characterization of cooperative bicarbonate uptake into chloroplast stroma in the green alga Chlamydomonas reinhardtii.
-
HLA3 localizes to the plasma membrane by immunofluorescence and membrane fractionation.
"Similarly, a notable enrichment of HLA3 was observed in the PM fraction. LCIA was highly enriched in the CE fraction, where CE protein CCP1 (30) was also enriched. From these results, we concluded that HLA3 and LCIA were localized to the PM and CE, respectively."
-
An HLA3 insertion mutant (complemented) has reduced Ci accumulation in very low CO2.
"These results indicated that HLA3 has a meaningful role in HCO3– uptake in VLC conditions."
-
Co-overexpression of HLA3 with LCIA in high CO2 increases Ci affinity and accumulation; HLA3 alone has a small effect.
"simultaneous overexpression of HLA3 with LCIA significantly increased Ci affinity/accumulation"
-
HLA3 and LCIA do not form a common complex; HLA3 runs at about 580 kDa in blue-native PAGE.
"These results strongly suggested that LCIA and HLA3 did not interact physically in vivo"
Expression activation and functional analysis of HLA3, a putative inorganic carbon transporter in Chlamydomonas reinhardtii.
-
dTALE-driven activation of HLA3 in high-CO2 cells increases Ci accumulation and Ci-dependent photosynthesis at very low CO2.
"Activation of HLA3 expression in high CO2 acclimated cells, where HLA3 is not expressed, resulted in increased Ci accumulation and Ci-dependent photosynthetic O2 evolution specifically in very low CO2 concentrations"
Introducing an algal carbon-concentrating mechanism into higher plants: location and incorporation of key components.
-
Venus-tagged HLA3 is in the plasma membrane in Chlamydomonas.
"LCI1: Venus and HLA3: Venus were in the plasma membrane."
-
HLA3 expressed in Xenopus oocytes reaches the cell surface and increases H14CO3- uptake 2.7-fold.
"Oocytes transformed with mLCIA: GFP or HLA3: GFP accumulated 2.0‐ and 2.7‐fold more 14C than water‐injected controls, respectively"
-
The transport mode (active or passive) of HLA3 remains unresolved.
"Further kinetic analyses will be required to determine the mode of action of these proteins (i.e. active vs. passive transport)."
A Spatial Interactome Reveals the Protein Organization of the Algal CO(2)-Concentrating Mechanism.
-
HLA3 co-purifies reciprocally with LCI1 and with the P-type ATPase ACA4.
"Unexpectedly, we found that HLA3 and LCI1 are found together in a complex."
Transcriptome-wide changes in Chlamydomonas reinhardtii gene expression regulated by carbon dioxide and the CO2-concentrating mechanism regulator CIA5/CCM1.
-
HLA3 is a CIA5-regulated, low-CO2-induced gene clustered with the candidate Ci transporter genes LCIA and LCI1.
"includes essentially all the genes for which there is either compelling evidence for a C i transport role for the gene product in the CCM ( LCIA , LCI1 , and HLA3 )"
Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Electronic Gene Ontology annotations created by transferring manual GO annotations between related proteins based on shared sequence features
Combined Automated Annotation using Multiple IEA Methods