Protein

Species

Identified genes

C4 accession number

Summary of light and developmental regulation

β-CA

Flaveria bidentis

CA1, CA2, CA3 (72, 131)

AY167113

N/A

Maize

CA1, CA2 (17)

U08403

Activity increases along the leaf developmental gradient from base to tip. In the dark, activity is less than 1% of that in the light and increases rapidly after a dark-to-light transition. However, its activity is not subject to dark inactivation

Sorghum

Tandem duplication:Sb03g029170,

Sb03g029180, Sb03g029190,

Sb03g029200 (141). Sb03g029170

has 13 exons and an internal repeat

structure and is likely a fusion of 2

neighbouring CA genes. The first

exon contains a chloroplast targeting

peptide. Sb03g029180 has only 6

exons and lacks the cTP.

Sb03g029200 is likely a pseudogene

because it is truncated and has a

DNA insertion as well as point

mutations. Sb03g029190 has a

normal gene structure but does not

group with C4 CA genes found in

maize when analyzed

phylogenetically

Sb03g029170 corresponds to two previously identified cDNAs, HHU69 and HHU22 (146). Expression of these cDNAs is light-inducible and restricted to M cells

PEPC

Flaveria trinervia

PpcA, PpcB, PpcC (44, 45, 99)

X61304

When the FtPpcA promoter is fused to uidA and transformed into F. bidentis, promoter activity spreads from leaf base to tip. Proximity of the M cell to the BS affects the intensity of staining, with greater distances resulting in little to no GUS

Maize

Pepc1, Pepc2, and Pepc3(111)

NM 001111948

PEPC expression is light regulated (89) and PEPC

localization becomes restricted to M cells during

development (64, 78). Light causes an increase in PEPC1 transcription and in the amount of heteronuclear and translatable RNA (37, 43, 53, 120). Regions 5_ to thePEPC1 gene have been implicated in its response to light. The nuclear factors PEP-I, MNFs, and Dof1&2 have been shown to bind the PEPC1 promoter and are likelyimportant for light regulation. Dof2 is thought to repress Dof1 in nonphotosynthetic tissues. Alterations in chromatin associated with PEPC1 have been implicated in the response to light

Sorghum

Sb10g021330 (141)

X17379, X63756

PEPC expression is responsive to a dark-to-light switch and under phytochrome control

MDH

Flaveria spp.

MDH (86)

F. bidensis: L40958

F. trinervia: U22533

N/A

Maize

MDH (88)

X16084

Transcript accumulation is light induced

Sorghum

MDH1, MDH2 arranged in tandem

(22, 71). Designated loci in genome:

Sb07g023920 and Sb07g023910,

respectively (141).

X53453, M31965

MDH1 is induced by light. MDH2 transcripts are

expressed in a more constitutive manner and are less abundant relative to MDH1

NADP-ME

F. trinervia and

F. bidentis

NADP-ME1 (ChlMe1),NADP-ME2

(ChlMe2) (76, 102)

F. trinervia:

AF288919

F. bidentis: AF288899

NADP-ME1 transcript accumulation is restricted to leaves,light regulated, and synchronized with the onset of C4 metabolism

Maize

NADP-ME1, NADP-ME2.

NADP-ME1 is also known as Me3

and Mod1 (109, 129)

NM 001111843

Transcripts are detectable in etiolated leaves but abundance increases fivefold upon greening. Accumulation is most marked in plastochrons 6 to 7. UV-B and red/far red light are involved in ME1 regulation in etiolated seedlings

Sorghum

Sb03g003230, plus two additional

orthologous pairs of genes

AY274836

N/A

PPDK

F. trinervia

PPDK

X57141

Accumulation of transcripts encoding plastidic transcript PPDK are light regulated

Maize

PPDK1 (encodes C4PPDKZM1 and

CYPPDKZM1), PPDK2(34, 82,

113)

NM 001112268

Synthesis of C4 PPDK protein is most significant at 2 to 4 cm from the base of the leaf (84). Elements −1300 to +72 of PPDK1 generate light-responsive expression in protoplasts

Sorghum

Sb09g019930, Sb01g031660

Sb09g019930 gene structure is similar to maize

SSU

F. bidentis

RbcS1, RbcS2

AY267350,

AY267351

Maize

RbcS multigene family(115)

ssu1 locus:

NM 001111824

RbcS expression is light regulated (89). Stimulation of

transcript abundance in response to light occurs within 24 h and RbcS transcripts accumulate coincident with basal to apical leaf development (84). SSU only accumulates in mature leaf tissue, but RbcS mRNA is detectable before the BS is fully differentiated. Transcripts of RbcS accumulate differentially in C3-(husk) and C4-(leaf) type

tissues

Sorghum

Sb05g003480, Sb08g001646

N/A

Amaranthus

Hypochondriacus

RbcS

X87171

Transfer to light leads to a large increase in abundance of RbcS transcripts and an association of RbcS transcripts with polysomes. During periods of extended darkness,rates of SSU synthesis decline more significantly than the abundance ofRbcS transcripts, although the transcripts remain attached to polysomes

LSU

Flaveria spp. and

A. hypochondriacus

rbcL

F. bidentis: X55830

A. hypochondriacus:

X51964

Light is required to induce high levels of rbcL accumulation but not to initiate transcription, indicating a developmental signal is necessary for expression. Unlike SSU, LSU accumulation in Amaranth cotyledons is similar in the dark

and light and precedes SSU detection. In leaves, patterns of rbcL accumulation overlap with those of RbcS

Maize

rbcL

ZemaCp032

rbcL expression is regulated by light and veinspacing

Sorghum

SobiCp030

N/A

Polypeptides of

PSII

Maize, sorghum,

sugar cane,

pennisetum,

F. trinervia

Plastid and nuclear encoded

During leaf development PSII activity and the abundance of transcripts encoding PSII components decrease in BS cells. Light intensity and environment appear to influence the degree to which PSII activity and accumulation is repressed in the BS of F. trinervia

NAD-ME

A. hypochondriacus

NAD-ME

U01162

NAD-ME is expressed very early in leaf development and is highly light-dependent, and run-ons show this is partly due to a light-stimulated increase in transcription. The rate of protein synthesis after transfer of light-grown leaves into the dark decreased more dramatically than the abundance of transcripts , indicating regulation at the level of

translation as well

PEPCK

Maize

PCK

AB018744

PCK is abundant in BS cells of maize, a NADP-ME C4 plant. The transcript accumulates to higher levels in the day than at night and increases over the course of seedling development

PPDK-RP

Maize

PDRP1

NM 001112403

N/A

Sorghum

Sb02g035190, tandem paralogues

Sb02g035200 and Sb02g035210

N/A

PEPC-kinase

(PPCK, PEPCk)

F. trinervia

PEPC-K, additional genes likely

AB065100

PEPC-K transcripts are detectable in the light but not during the night. Expression is higher in F. trinervia than in the C3 F. pringlei

Maize

PPCK1, PPCK2, PPCK3, PPCK4

NM 001112338

PPCK1 transcripts are most abundant in the light. PPCK2 transcripts preferentially accumulate in BS cells in the dark. PPCK3 and PPCK4 transcripts are less abundant than PPCK1 and -2

Sorghum

Sb04g036570 (PPCK1),

Sb04g026490 (PPCK2),

Sb06g022690 (PPCK4)

DQ386731

PPCK1 expression is light regulated