Os04g0690800

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Function

PsbS is associated with the reversible de-epoxidation of violaxanthin to zeaxanthin, the so-called xanthophyll cycle.

PsbS regulates CO2 assimilation rate when light fluctuates. Its content has significant influence on the chloroplasts protective energy dissipation (chloroplastic protective energy dissipation, qE). Chl fluorescence as energy quenching(qE) depends on the presence of the PsbS subunit.

Expression

To confirm the RNAi effect, the expression ofpsbS genes in T2 transgenic rice was analyzed (Fig. 1A). Quantitative reverse transcription–PCR (RT–PCR) analysis revealed that the amounts of bothpsbS1 andpsbS2 transcripts were significantly reduced in the �1&2-1 and �1&2-2 lines. On the other hand,psbS gene expression in the�2 line was not distinguishable from that in the wild type, suggesting that gene silencing of psbS2 in the�2 line did not work. Immunoblot analysis using anti-PsbS antibody showed that the accumulation of PsbS protein was not detected in the �1&2-1 and �1&2-2 lines(Fig. 1B). Two isoproteins derived from each of the homolog genes could not be distinguished by SDS–PAGE analysis. These results indicate that the expression of psbS genes in the� 1&2-1 and� 1&2-2 lines was successfully silenced by RNAi[1].File:Expression of psbS genes in transgenic plants.png

sequence

Two psbS genes were found in the rice genome by BLASTN in the NCBI database based on the sequence of psbSofArabidopsis thaliana. PsbS2 is located on chromosome.The number of registered expressed sequence tags (ESTs) in leaves (total ESTs, 171,890) of psbS1 was 50, while that of psbS2 was six based on the NCBI UniGene database (http://www.ncbi.nlm.nih.gov/unigene),suggesting that psbS1 is expressed more than psbS2.Phylogenetic analysis showed that PsbS1 had high sequence homology with proteins from other Gramineae plants, while PsbS2 rather resembled proteins from dicot species ,although the bootstrap values are too low to draw any unambiguous conclusions regarding the rather unexpected position of psbS2.

Labs working on this gene

There are many labs working on PsbS.Demmig-Adams and Hendrickson both have their own models on this study. EST, expressed sequence tag; Fm(Fm0), themaximum fluorescence achieved with a saturating light pulse in the dark (or in the light);Fo (Fo0), the minimumfluorescence achieved under the measuring light in the dark(or in the light); Fs, steady-state fluorescence in the light; �D,the quantum rate of absorbed light energy in PSII allocated to Dissipationin the Demmig-Adams model; �E , the quantum rate of absorbed light energy in PSII allocated to Exess in the Demmig-Adams model; �f,D, the quantum yield of basic dissipation in the Hendrickson model;�NPQ, the quantum yield of light-inducible dissipation in the Hendrickson model.

References

Satoshi Ishida[1,4], Ken-ichi Morita[1,4], Masahiro Kishine[1], Atsushi Takabayashi[1], Reiko Murakami[1],Satomi Takeda[2], Ko Shimamoto[3], FumihikoSat[1] and Tsuyoshi Endo[1].Allocation of Absorbed Light Energy in PSII to Thermal Dissipations in the Presence or Absence of PsbS Subunits of Rice[J]. Cell Physiol (2011), 52 (10): 1822-1831.