e-journal

Significant involvement of PEP-CK in carbon assimilation of C4 eudicots

---

† Background and Aims:
C4 eudicot species are classified into biochemical sub-types of C4 photosynthesis based on the principal decarboxylating enzyme. Two sub-types are known, NADP-malic enzyme (ME) and NAD-ME; however, evidence for the occurrence or involvement of the third sub-type (phosphoenolpyruvate carboxykinase; PEP-CK) is emerging. In this study, the presence and activity of PEP-CK in C4 eudicot species of Trianthema and Zaleya (Sesuvioideae, Aizoaceae) is clarified through analysis of key anatomical features and C4 photosynthetic enzymes.

† Methods:
Three C4 species (T. portulacastrum, T. sheilae and Z. pentandra) were examined with light and transmission
electron microscopy for leaf structural properties. Activities and immunolocalizations of C4 enzymes
were measured for biochemical characteristics.

† Key Results:
Leaves of each species possess atriplicoid-type Kranz anatomy, but differ in ultrastructural features.
Bundle sheath organelles are centripetal in T. portulacastrum and Z. pentandra, and centrifugal in T. sheilae. Bundle sheath chloroplasts in T. portulacastrum are almost agranal, whereas mesophyll counterparts have grana. Both T. sheilae and Z. pentandra are similar, where bundle sheath chloroplasts contain well-developed grana while mesophyll chloroplasts are grana deficient. Cell wall thickness is significantly greater in T. sheilae than in the other species. Biochemically, T. portulacastrum is NADP-ME, while T. sheilae and Z. pentandra are NAD-ME. Both T. portulacastrum and Z. pentandra exhibit considerable PEP-CK activity, and immunolocalization studies show dense and specific compartmentation of PEP-CK in these species, consistent with high PEP-CK enzyme activity.

†Conclusions:
Involvement of PEP-CK in C4 NADP-ME T. portulacastrum and NAD-ME Z. petandra occurs irrespective of biochemical sub-type, or the position of bundle sheath chloroplasts. Ultrastructural traits, including
numbers of bundle sheath peroxisomes and mesophyll chloroplasts, and degree of grana development in
bundle sheath chloroplasts, coincide more directly with PEP-CK recruitment. Discovery of high PEP-CK activity
in C4 Sesuvioideae species offers a unique opportunity for evaluating PEP-CK expression and suggests the
possibility that PEP-CK recruitment may exist elsewhere in C4 eudicots.

Key words: Aizoaceae, C4 photosynthesis, granal development, Kranz anatomy, NADP-ME sub-type, NAD-ME
sub-type, PEP-CK sub-type, Sesuvioideae, thylakoid, Trianthema portulacastrum, Trianthema sheilae,
Zaleya pentandra.

---

Ketersediaan

Tidak ada salinan data

Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

-

Penerbit

Oxford : Oxford University Press on behalf of the Annals of Botany Company., 2013

Deskripsi Fisik

Annals of Botany 111: 577–589, 2013

Bahasa

English

ISBN/ISSN

-

Klasifikasi

-

Tipe Isi

-

Tipe Media

-

Tipe Pembawa

-

Edisi

111: 2013

Subjek

EKOFISIOLOGI TANAMAN

Info Detail Spesifik

-

Pernyataan Tanggungjawab

agus

Versi lain/terkait

Lampiran Berkas

Komentar

---

Anda harus masuk sebelum memberikan komentar