April
2003
, Volume
16
, Number
4
Pages
281
-
288
Authors
Tomomi
Nakagawa
,
1
Tomoko
Izumi
,
2
Mari
Banba
,
2
Yosuke
Umehara
,
3
Hiroshi
Kouchi
,
3
Katsura
Izui
,
1
,
2
and
Shingo
Hata
1
,
2
Affiliations
1Laboratory of Plant Physiology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; 2Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; 3National Institute of Agrobiological Sciences, Tsukuba, Ibakaki 305-8602, Japan
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RelatedArticle
Accepted 3 December 2002.
Abstract
Phosphoenolpyruvate carboxylases (PEPCs), one form of which in each legume species plays a central role in the carbon metabolism in symbiotic root nodules, are activated through phosphorylation of a conserved residue by a specific protein kinase (PEPC-PK). We characterized the cDNAs for two PEPC isoforms of Lotus japonicus, an amide-translocating legume that forms determinate nodules. One gene encodes a nodule-enhanced form, which is more closely related to the PEPCs in amide-type indeterminate nodules than those in ureide-type determinate nodules. The other gene is expressed in shoots and roots at a low level. Both forms have the putative phosphorylation site, Ser11. We also isolated a cDNA and the corresponding genomic DNA for PEPC-PK of L. japonicus. The recombinant PEPC-PK protein expressed in Escherichia coli phosphorylated recombinant maize C4-form PEPC efficiently in vitro. The level of mRNA for PEPC-PK was high in root nodules, and those in shoots and roots were also significant. In situ hybridization revealed that the expression patterns of the transcripts for PEPC and PEPC-PK were similar in mature root nodules, but were different in emerging nodules. When L. japonicus seedlings were subjected to prolonged darkness and subsequent illumination, the activity of PEPC-PK and the mRNA levels of both PEPC and PEPC-PK in nodules decreased and then recovered, suggesting that they are regulated according to the amounts of photosynthates transported from shoots.
JnArticleKeywords
Additional keywords:
carbon metabolism,
gene expression,
symbiotic root nodule.
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© 2003 The American Phytopathological Society