The promoters of two carboxylases in a C4 plant (maize) direct cell‐specific, light‐regulated expression in a C3 plant (rice)

Makoto Matsuoka, Junko Kyozuka, Ko Shimamoto, Yuriko Kano‐Murakami

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88 Citations (Scopus)

Abstract

C4 plants have two carboxylases which function in photosynthesis. One, phosphoenolpyruvate carboxylase (PEPC) is localized in mesophyll cells, and the other, ribulose bisphosphate carboxylase (RuBPC) is found in bundle sheath cells. In contrast, C3 plants have only one photosynthetic carboxylase, RuBPC, which is localized in mesophyll cells. The expression of PEPC in C3 mesophyll cells is quite low relative to PEPC expression in C4 mesophyll cells. Two chimeric genes have been constructed consisting of the structural gene encoding β‐glucuronidase (GUS) controlled by two promoters from C4 (maize) photosynthetic genes: (i) the PEPC gene (pepc) and (ii) the small subunit of RuBPC (rbcS). These constructs were introduced into a C3 cereal, rice. Both chimeric genes were expressed almost exclusively in mesophyll cells in the leaf blades and leaf sheaths at high levels, and no or very little activity was observed in other cells. The expression of both genes was also regulated by light. These observations indicate that the regulation systems which direct cell‐specific and light‐inducible expression of pepc and rbcS in C4 plants are also present in C3 plants. Nevertheless, expression of endogenous pepc in C3 plants is very low in C3 mesophyll cells, and the cell specificity of rbcS expression in C3 plants differs from that in C4 plants. Rice nuclear extracts were assayed for DNA‐binding protein(s) which interact with a cis‐regulatory element in the pepc promoter. Gel‐retardation assays indicate that a nuclear protein with similar DNA‐binding specificity to a maize nuclear protein is present in rice. The possibility that differences in pepc expression in a C3 plant (rice) and C4 plant (maize) may be the result of changes in cis‐acting elements between pepc in rice and maize is discussed. It also appears that differences in the cellular localization of rbcS expression are probably due to changes in a trans‐acting factor(s) required for rbcS expression.

Original languageEnglish
Pages (from-to)311-319
Number of pages9
JournalThe Plant Journal
Volume6
Issue number3
DOIs
Publication statusPublished - 1994 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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