Effects of overexpression of the Rubisco small subunit gene under the control of the Rubisco activase promoter on Rubisco contents of rice leaves at different positions

Abstract C4 plants, such as maize, strictly compartmentalize Rubisco to bundle sheath chloroplasts. The molecular basis for the restriction of Rubisco from the more abundant mesophyll chloroplasts is not fully understood. Mesophyll chloroplasts transcribe the Rubisco large subunit gene, and when normally quiescent transcription of the nuclear Rubisco small subunit gene family is overcome by ectopic expression, mesophyll chloroplasts still do not accumulate measurable Rubisco. Here we show that a combination of five ubiquitin promoter-driven nuclear transgenes expressed in maize leads to mesophyll accumulation of assembled Rubisco. These encode the Rubisco large and small subunits, Rubisco Assembly Factors 1 and 2, and the assembly factor Bundle Sheath Defective 2. In these plants Rubisco large subunit accumulates in mesophyll cells, and appears to be assembled into holoenzyme capable of binding the substrate analog CABP. Isotope discrimination assays suggest, however, that mesophyll Rubisco is not participating in carbon assimilation in these plants, most likely due to a lack of the substrate ribulose 1,5-bisphosphate and/or Rubisco activase. Overall, this work defines a minimal set of Rubisco assembly factors in planta and may help lead to methods of regulating the C4 pathway.

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Effects of Overproduction of Rubisco Activase on Rubisco Content in Transgenic Rice Grown at Different N Levels

International Journal of Molecular Sciences ◽

10.3390/ijms21051626 ◽

2020 ◽

Vol 21 (5) ◽

pp. 1626 ◽

Cited By ~ 3

Author(s):

Mao Suganami ◽

Yuji Suzuki ◽

Eri Kondo ◽

Shinji Nishida ◽

So Konno ◽

...

Keyword(s):

Oryza Sativa ◽

Transgenic Rice ◽

Oryza Sativa L ◽

Rubisco Activase ◽

Small Subunit ◽

Wild Type ◽

N Supply ◽

Rubisco Small Subunit ◽

N Concentration ◽

Rbcs Genes

It has been reported that overproduction of Rubisco activase (RCA) in rice (Oryza sativa L.) decreased Rubisco content, resulting in declining photosynthesis. We examined the effects of RCA levels on Rubisco content using transgenic rice with overexpressed or suppressed RCA under the control of different promoters of the RCA and Rubisco small subunit (RBCS) genes. All plants were grown hydroponically with different N concentrations (0.5, 2.0 and 8.0 mM-N). In RCA overproduced plants with > 2-fold RCA content (RCA-HI lines), a 10%–20% decrease in Rubisco content was observed at 0.5 and 2.0 mM-N. In contrast, at 8.0 mM-N, Rubisco content did not change in RCA-HI lines. Conversely, in plants with 50%–60% increased RCA content (RCA-MI lines), Rubisco levels remained unchanged, regardless of N concentration. Such effects on Rubisco content were independent of the promoter that was used. In plants with RCA suppression to < 10% of the wild-type RCA content, Rubisco levels were increased at 0.5 mM-N, but were unchanged at 2.0 and 8.0 mM-N. Thus, the effects of the changes in RCA levels on Rubisco content depended on N supply. Moreover, RCA overproduction was feasible without a decrease in Rubisco content, depending on the degree of RCA production.

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CRISPR/Cas9-induced monoallelic mutations in the cytosolic AGPase large subunit gene APL2 induce the ectopic expression of APL2 and the corresponding small subunit gene APS2b in rice leaves

Transgenic Research ◽

10.1007/s11248-018-0089-7 ◽

2018 ◽

Vol 27 (5) ◽

pp. 423-439 ◽

Cited By ~ 5

Author(s):

Lucía Pérez ◽

Erika Soto ◽

Gemma Villorbina ◽

Ludovic Bassie ◽

Vicente Medina ◽

...

Keyword(s):

Large Subunit ◽

Ectopic Expression ◽

Small Subunit ◽

Subunit Gene ◽

Rice Leaves

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Cell-Specific Expression of Rubisco Small Subunit and Rubisco Activase Genes in C3 and C4 Species of Atriplex

Functional Plant Biology ◽

10.1071/pp9920089 ◽

1992 ◽

Vol 19 (1) ◽

pp. 89 ◽

Cited By ~ 7

Author(s):

GS Hudson ◽

RE Dengler ◽

PW Hattersley ◽

G Dengler

Keyword(s):

In Situ Hybridisation ◽

Rubisco Activase ◽

Small Subunit ◽

Bundle Sheath ◽

Specific Expression ◽

Bisphosphate Carboxylase ◽

C4 Species ◽

Rubisco Small Subunit ◽

Rbcs Gene

In situ hybridisation techniques have been used to determine the distribution of mRNAs for ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco: EC 4.1.1.39) and Rubisco activase in leaves of Atriplex patula L. (C3) and A. rosea L. (C4). In A. patula, mRNA for Rubisco small subunit (encoded by the rbcS gene family) was found to accumulate in the mesophyll and bundle sheath, while in A. rosea it accumulated in the bundle sheath only, as shown previously for the C4 monocot Zea mays L. The spatial distribution of rca transcripts for Rubisco activase paralleled that for the rbcS transcripts in both C3 and C4 Atriplex species, providing evidence that Rubisco activase is required in cells only where Rubisco is present.

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