Botanical Studies (2006) 47: 45-50.

*

Corresponding author: e-mail: hshige@agbi.tsukuba.ac.jp;

Tel & Fax: +81-29-853-4603.

BIOCHEMISTRY

A glycolipid involved in flower bud formation of

Arabidopsis thaliana

Yosuke HisamaTsu

1

, Nobuharu GOTO

2

, Koji HasEGaWa

1

, and Hideyuki sHiGEmORi

1,

*

1

Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan

2

Department of Biology, Miyagi University of Education, Sendai 980-0845, Japan

(Received December 21, 2004; accepted september 27, 2005)

ABSTRACT.

We searched for bioactive substances involved in flower bud formation of Arabidopsis

thaliana. some significantly decreasing HPLC peaks were detected in the extract of flower buds-forming

A. thaliana compared with that of the non-flower bud-forming stage. Compound 1, which corresponded to

the most decreased HPLC peak, was isolated from aerial parts of A. thaliana. From NmR and ms data,

compound 1 was identified as one of the monogalactosyl diacylglyceride (mGDG). Compound 1 induced

flower bud formation of A. thaliana exposed to long day condition for only 1 day. These results suggest that

compound 1 as a precursor or a substrate of flower bud-forming substances plays important roles in the flower

bud formation of A. thaliana.

Keywords: Arabidopsis thaliana; Bioactive substance; Flower bud formation; Long day condition; mGDG;

short day condition.

IntroductIon

Flower bud formation is one of the most important

physiological process for higher plants, and the flowering

time is influenced by photoperiod, vernalization, drought

stress, and so on. Chailakhyan demonstrated that

flowering was regulated by the bioactive substances,

which were produced in leaves that were subjected

to favorable photoperiods, and the substances were

transported to the shoot apex to induce flower bud

formation. He named the substances "flower-inducing

hormone" or "florigen" (Chailakhyan, 1936). Since then,

studies on isolation of substances inducing flower bud

formation have been carried out with a large number

of plant species. For example, when the water solution

prepared by immersing Lemna paucicostata exposed

to drought, heat, or osmotic stress, were incubated with

(-)-norepinephrine, the water solution showed strong

flower inducing activity of L. paucicostata (Takimoto

et al., 1994). They found that FN1, the tricyclic α-ketol

fatty acid derived from (-)-norepinephrine and 9, 10-ketol-

octadecadienoic acid (KODA), induced flower formation

of Lemna (Yamaguchi et al., 2001). On the other hand,

to analyze the molecular processes that initiate flower

bud formation and trigger the change from vegetative

to reproductive growth, biologists have performed

intensive genetic studies of flowering time in model plant

A. thaliana. as a result, there was discovery of many

genes about the regulation of flowering time and the

development of a lot of genetic models (Bastow and Dean,

2003). However, bioactive substances involved in flower

bud formation of A. thaliana have been hardly reported.

In this paper, we report the isolation and identification of

a bioactive substance (compound 1) involved in flower

bud formation of A. thaliana and the flower buds-forming

activity of compound 1.

MAterIAlS And MethodS

equipment

Optical rotations were measured with a JasCO

DiP-370 polarimeter.

1

H an d

13

C NmR spectra were

measured and recorded on a Buker aVaNCE-500 in

CD

3

OD. The resonances of CD

3

OD at δ

H

3.35 ppm and

δ

C

49.8 ppm were used as internal standards for NmR

spectra. Esims were recorded on a Waters platform

LC. HPLC was performed using a system composed

of a TOsOH DP-8020 pump and a TOsOH PD-8020

photodiodearray detector or a TOsOH Ri-8021 refractive

index detector.

Plant materials

The seeds of Arabidopsis thaliana cv. Columbia

were provided by the sendai Arabidopsis seed stock

Center (sassC, Japan). The seeds were immersed in

the water for 2 days before sowing on rock wool (Rock

fiber, NITTOBO, Japan). They have been cultured in the

growth container (24°C, ca. 3,800 lux) under short day

condition (8 h-light and 16 h-dark, sD) for 26 or 30 days.

46

Botanical Studies, Vol. 47, 2006

Figure 1. HPLC chromatograms of groups i, ii, and iii. Group

i: grown under long day conditions (16 h-light and 8 h-dark, LD,

ca. 2,500 lux) until the flower bud formation, Group II: grown

under sD and exposed to LD for 3 days just before extraction,

and Group iii: grown under sD throughout the course of the

experiment. They were extracted with meOH and partitioned

between EtOac and H

2

O. The EtOac-soluble materials were

analysed by HPLC. This experiment was repeated 3 times.

hPlc analyses of the extracts of groups I, II,

and III

Arabidopsis thaliana were cultured at 24°C for 26 days

under sD, and they were divided into groups i, ii, and

iii. Group i was grown under long day conditions (16

h-light and 8 h-dark, LD, ca. 2,500 lux) until the flower

bud formation, group ii was grown under sD and exposed

to LD for 3 days just before extraction, and group iii was

grown under sD throughout the course of this experiment.

The aerial parts of each group were frozen with liquid

N

2

, and ground to a fine powder in a mortar, and then

they were extracted with meOH for 3 times. The meOH

extracts were evaporated to dryness in vacuo at 30°C and

the residue was partitioned between EtOac and H

2

O. The

each equivalent amount of EtOAc-soluble material was

analysed by a reversed-phase HPLC (ODs-80Ts, φ4.6×

250 mm, TOsOH, uV detection at 195 nm) with H

2

O-

CH

3

CN under linear gradient conditions at 0.8 ml/min

(aqueous portion: 0 to 100% CH

3

CN at 1%/min, at 100%

CH

3

CN for 10 min, EtOAc-soluble portion: 50 to 100%

CH

3

CN at 1%/min, at 100% CH

3

CN for 30 min). Further

HPLC analysis (same as above) was under the condition at

95% CH

3

CN (Figure 1).

Isolation and structure identification of

compound 1

The aerial parts of A. thaliana were extracted with

meOH (200 mL), and the meOH extracts were evaporated

to dryness in vacuo at 30°C. Then the residue was

partitioned between EtOac and H

2

O. The EtOac-

soluble portion was applied to a reversed-phase column

(TOYOPAK ODS M, TOSOH, 100% CH

3

CN) to afford

a glycolipids fraction, which was purified by a reversed-

phase HPLC (ODs-80Ts, φ4.6×250 mm, TOSOH, 95%

CH

3

CN at a flow rate of 0.8 ml/min, UV detection at 195

nm). From 0.78 g of aerial parts of A. thaliana, 0.3 mg of

compound 1 was obtained.

The mass spectrum of compound 1 gave m/z 769

(m+Na)

+

.

1

H NmR (CD

3

OD): δ 1.03 (6H, t, J = 5.4 Hz),

1.38 (6H, m), 1.67 (2H, m), 2.13 (4H, m), 2.37 (2H, m),

2.86 (4H, m), 3.50 (1H, dd, J = 3.2 and 9.7 Hz, 3’-H), 3.55

(2H, m, 2’, 5’-H), 3.75 (1H, dd, J = 5.2 and 10.7 Hz, sn-

3-Hb, overlapped with 6’-H), 3.79 (2H, m, 6’-H), 3.86

(1H, d, J = 3.2 Hz, 4’-H), 4.04 (1H, dd, J = 5.5, 10.9 Hz,

sn-3-Ha), 4.26 (1H, dd, J = 6.7 and 12.0 Hz, sn-1-Hb,

overlapped with 1’-H), 4.27 (1H, d, J = 7.5 Hz, 1’-H), 4.49

(1H, dd, J = 2.8 and 12.0 Hz, sn-1-Ha), 5.31 (1H, m, sn-

2-H), and 5.40 (12H, m, 7’’-H, 8’’-H, 10’’-H, 11’’-H, 13’’

-H, 14’’-H, 9’’’-H, 10’’’-H, 12’’’-H, 13’’’-H, 15’’’-H, 16’’’

-H).

13

C NmR (CD

3

OD): δ 105.8 (C-1’), 72.8 (C-2’), 75.3

(C-3’), 70.7 (C-4’), 77.3 (C-5’), 62.9 (C-6’), 64.5 (sn-

1-C), 72.2 (sn-2-C), 69.2 (sn-3-C), 22.04, 22.17 (C-15’’,

C-17’’’), 26.42, 26.53, 26.92, 27.04 (C-9’’, C-11’’’, C-12’’,

C-14’’’), 28.57, and 28.69 (C-6’’, C-8’’’).

Enzymatic hydrolysis of compound 1. a solution of

compound 1 (1 mg) and lipase type Xi (0.72 units, sigma)

in boric acid – borax buffer [0.63 mL, containing Triton

X-100 (2.5 mg), pH 7.7] was stirred at 38°C for 12 h. The

reaction was quenched with AcOH (0.1 mL) and then

EtOH was added to the reaction mixture. The solvent was

removed by N

2

gas and the residue was purified by a silica

gel column (CHCl

3

/MeOH, 12:1→7:1) to afford linolenic

acid and sn2-O -(hexadecatrienoyl)-monogalactosyl

glyceride (morimoto et al., 1995).

Determination of absolute configuration at C-2 in

compound 1. a solution of compound 1 (9.6 mg) and

NaOMe (10 equiv.) in anhyd. MeOH (0.1 mL) was stirred

at room temperature for 1 h. The reaction mixture was

partitioned between hexane and water and the water-

soluble materials were purified by a C

18

column (sep-Pak

C

18

cartridge 12 CC, Waters, H

2

O) and HPLC (TsKgel

amide-80, φ4.6×250 mm, TOSOH, 75% CH

3

CN, flow rate:

0.8 mL/min, RI detection) to give the β-galactosylglycerol

(2, 1.75 mg, 54%). The absolute configuration of 2 was

determined by comparison with the optical rotation (son

et al., 2001).

long day treatment under weak light

Arabidopsis thaliana were cultured at 24°C for 26 days

under sD. some plants were grown under sD throughout

the course of the experiment. The others were cultured for

several days under long day conditions (16 h-light and 8

h-dark, LD, ca. 2,500 lux), and then were grown under sD

until flower bud formation. The days for forming flower

bud was measured individually and averaged. means ±

sE showed of 3 replicates of 5 plants.

Bioassay

Thirty-day-old A. thaliana plants cultured at 24°C

under sD were used for bioassay. Before application,

one group of the assayed plants was exposed to LD for

HISAMATSU et al. — A bioactive substance of

A. thaliana

47

Figure 2. 2D NmR correlations of compound 1 (A) and β-galactosyl glycerol (2) derived from compound 1 (B).

one day (LD-1). it was shown that exposing to long

day condition for only 1 day (LD-1) give the plants only

slight promotion of forming flower bud (Figure 1). Then,

compound 1 in 50% aqueous acetone solutions of several

concentrations was applied to the center of rosette leaves

using microsyringe at intervals of 7 days. Twenty-days

after the onset of application, the number of plants formed

flower bud was counted. This experiment was repeated

twice.

reSultS

The aerial parts of A. thaliana in groups i, ii, and

iii were extracted with meOH, and the extracts were

partitioned between EtOac and H

2

O. The EtOac-soluble

materials were analysed by HPLC. some decreased peaks

were observed in t

R

50-80 min fraction of EtOac-soluble

materials obtained from group i in comparison with

those of groups ii and iii, while no increased peaks were

observed. as the result of further analysis, peak 1 was

most decreased in HPLC chromatogram of group i (Figure

1).

To identify the structure of compound 1 corresponded

to peak 1, the aerial parts of A. thaliana were extracted

with meOH, and the extract was partitioned between

EtOac and H

2

O. The EtOac-soluble portion was

separated by a reversed-phase column and C

18

HPLC to

afford compound 1.

The Esims of compound 1 showed a pseudomolecular

ion peak at m/z 769 (m+Na)

+

. The gross structure of

compound 1 was deduced from detailed analysis of the

1

H and

13

C NmR data aided with 2D NmR experiments

(

1

H-

1

H COsY, HmQC, and HmBC). The

13

C NmR data

of compound 1 indicated that the molecule possessed two

ester carbonyl carbons, six disubstituted olefins, one acetal

carbon, five oxymethines, three oxymethylenes, eighteen

methylenes, and two methyl groups. The

1

H-

1

H COsY

connectivities of C-1 to C-3 and C-1’ to C-6’ indicated the

presence of a glycerol and a sugar component. The sugar

was assigned to be galactose by NOEsY correlations of

H-1’ to H-3’ and H-5’ and H-4’ to H-3’ and H-5’ and the

1

H-

1

H coupling constants (J

1’, 2’

= 7.3 Hz, J

2’, 3’

= 7.4 Hz, J

3’,

4’

= 2.5 Hz, J

4’, 5’

= ~0 Hz). HMBC correlations of H-1’ to

C-3 (δ

C

69.2) and H-3a and H-3b to C-1’(δ

C

105.8) and the

coupling constant (J

1’, 2’

= 7.3 Hz) of the anomeric proton

(H-1’) at δ

H

4.27 revealed that compound 1 possessed a

β-galactosyl glycerol moiety.

The

1

H-

1

H COSY connectivities of C-2’’ to C-16’’

and C-2’’’ to C-18’’’ indicated the presence of two fatty

acids which contained three double bonds, respectively.

Z-Genometiries of six double bonds at C-7’’-C-8’’, C-10’’

-C-11’’, C-13’’-C-14’’, C-9’’’-C-10’’’, C-12’’’-C-13’’’, and

C-15’’’-C-16’’’ were deduced from the carbon chemical

shifts (δ

C

< 30) of allylic carbons (Gunstone et al., 1977).

The two fatty acids were presumed to be octadecatrienoic

acid and hexadecatrienoic acid judging from Esims of

compound 1. HmBC correlations of Ha-1 and Hb-1 to

ester carbonyl carbon (δ

C

175.5 or 175.1) and chemical

shifts (δ

H

5.31; δ

C

72.2) of C-2 indicated that the linolenic

acid and hexadecatrienoic acid connected to C-1 and

C-2. In order to define the locations of these fatty acids

in the β-galactosyl glycerol moiety of compound 1,

we applied enzymatic hydrolysis. The lipase type XI

(Sigma)-catalyzed hydrolysis of compound 1 afforded

sn2-O -(hexadecatrienoyl)-monogalactosyl glyceride

and linolenic acid (morimoto et al., 1995). Therefore,

compound 1 was identified as sn1-O-(octadecatrienoyl)-

sn2-O-(hexadecatrienoyl)-monogalactosyl diglyceride

(Figure 2). The absolute configuration at C-2 in the

β-galactosylglycerol (2 ), which was derived from

compound 1 with NaOme presumed to be R, from the

basis of comparison of the optical rotation ([α]

D

-8°) of 2

with the reported values ([α]

D

-7° for C-2 R and [α]

D

+2°

for C-2 s) (son et al., 2001).

and next, we applied compound 1 to A. thaliana to

examine its affection in flower bud formation. Before

assay, we measured how long it took for forming flower

buds of A. thaliana under light conditions described in

materials and methods. as shown in Figure 3, A. thaliana

under LD for one day acquired about 23 days for forming

flower buds, but the plants exposed LD for 3 days longer

took about 15 days (Figure 3). When the solution of

48

Botanical Studies, Vol. 47, 2006

Table 1. The effect of compound 1 on flower bud formation.

Flower-bud forming plants

a

assayed plants

Control

b

3 (14%)

21

50% acetone

b

4 (20%)

20

Compound 1 (10 ppm)

7 (47%)

15

Compound 1 (100 ppm)

8 (53%)

15

Compound 1 (1,000 ppm)

11 (58%)

19

a

Number of flower-bud forming plants at twenty-days after the application of test solution to the assayed plants.

b

Control cultures were applied for nothing, an equal volume of 50% acetone (as negative control).

compound 1 in 50% aqueous acetone solutions of several

concentrations applied to the center of rosette leaves of

assayed plants, which were exposed to LD for one day just

before onset of the bioassay, the 58% of the plants applied

compound 1 at 1,000 ppm formed flower bud, whereas

only 14% and 20% of the plants applied for nothing or

50% acetone have flower bud (Table 1). On the other

hand, flower bud of the plants not exposed to LD were not

promoted by compound 1 (data not shown).

dIScuSSIon

in Arabidopsis thaliana, large amount of studies on

flower bud formation from genetic point of view have

been carried out. However, bioactive substances involved

in flowering of A. thaliana have been hardly reported.

in this study, therefore, we exhibited the isolation of

bioactive substances involved in flower bud formation of

A. thaliana.

The aerial parts of A. thaliana in groups i, ii, and

iii were extracted with meOH, and the extracts were

partitioned between EtOac and H

2

O. The EtOac-soluble

materials were analysed by HPLC. some decreased

peaks were observed in t

R

50-80 min fraction of EtOac-

soluble materials obtained from group i in comparison

with those of groups ii and iii, while increased peaks

weren’t observed. The decrease of peak 1 after flower

bud formation suggested that the substance including

peak 1 was metabolized to bioactive substance (s) when

flower bud was formed and in groups II and III, the peak

1 was not decreased as they were not formed flower bud.

Therefore, we further separated the fraction to afford

the substance of peak 1, which was named compound 1

(Figure 1). as a result, sn1-O-(octadecatrienoyl)-sn2-

O -(hexadecatrienoyl)-monogalactosyl diglyceride (1),

which corresponded to the most decreased HPLC peak,

was isolated from EtOac-soluble materials of A. thaliana

(Figure 2).

and next, we measured how long it took for forming

flower buds of A. thaliana under light conditions described

in materials and methods. it took about 23 days until

the flower buds under LD for one day were formed, but

the flower buds under LD for 3 days longer were formed

after about 15 days from the start of LD treatment (Figure

Figure 3. The effects of long day treatment related to flower

buds formation. sD: grown under short day condtions (8 h-light

and 16 h-dark, sD, ca. 3,800 lux) throughout the course of

the experiment, LD-1~7: cultured for 1-7 days under long day

conditions (16 h-light and 8 h-dark, LD, ca. 2,500 lux), and

were backed to sD, C-LD: cultured under LD until form ing

flower bud. The days for forming flower bud was measured

individually and averaged. means ± sE showed of 3 replicates

of 5 plants.

3). it suggested that exposing to LD for one day was

not enough for A. thaliana to change from vegetative to

reproductive growth under the long day conditions, and

slightly promoted the flower buds formation. Therefore

we assayed compound 1 to the plants exposed LD for one

day.

The solution of compound 1 in 50% aqueous acetone

of several concentrations was applied to the center of

rosette leaves of assayed plants that exposed to LD for one

day just before onset of the bioassay, and their effects on

flower bud formation was tested (Table 1). Compound

1 induced significantly flower bud formation, whereas

flower bud formation of the plants applied for nothing or

50% acetone wasn’t promoted. On the other hand, flower

bud of the plants not exposed to LD was not induced by

compound 1 (data not shown). These results suggest that

compound 1 is metabolized to the bioactive substance

(s) inducing flower bud by exposed to LD, and which

compound 1 was not metabolized to those by not exposed

to LD. so it envisaged that compound 1 is the precursor

HISAMATSU et al. — A bioactive substance of

A. thaliana

49

or the substrate of flower bud-inducing substance (s).

Compound 1 may play important roles in flower bud

formation of A. thaliana.

Compound 1 is one of monogalactosyl diglycerides

(mGDG), which are major constituents of the chloloplast

membrane in plants and recently, they were draw much

attention because of their various biological activity.

For example, mGDG is the stores of fatty acids that

are substrates of various bioactive substances, such as

jasmonic acid, 9, 10-ketol-octadecadienoic acid (KODa),

sn1-O-(12-oxophytodienoyl)-sn2-O-(hexadecatrienoyl)-

monogalactosyl glyceride (mGDG-O), and arabidopsides

a and B (Vick and Zimmerman, 1984; Yokoyama

et al., 2000; stelmach et al., 2001; Hisamatsu et al.,

2003). Jasmonic acid is one of the phytohormone which

stimulates or inhibits several events in plant growth and

development, while KODa was known to related to

flower induction of Lemna paucicostata and Pharbitis

nil (Miersch et al., 1999; Suzuki et al., 2003). MGDG-O

and arabidopsides a and B are rare mGDG containing

OPDa and/or dn-OPDa, which are precursors of

jasmonic acid (Baertschi et al., 1988; Weber et al., 1997).

Furthermore, as compound 1 induced flower bud of the

plants exposed to LD-1, it suggested bioactive substances

regulating flower bud formation of A. thaliana is also one

of the metabolites of mGDG. We are now studying the

substances derived from MGDG and their effect for flower

bud formation.

lIterAture cIted

Baertschi, s .W., C.D. ingram, T.m. Harris , and a.R. Brash.

1988. absolute configuration of cis-12-oxophytodienoic

aci d of fla xs eed: im plic at ions for the me cha nis m of

biosynthesis from the 13(S)-hydroperoxide of linolenic

acid. Biochemistry 27: 18-24.

Bastow, R. and C. Dean. 2003. Plant sciences. Deciding when to

flower. Science 302: 1695-1696.

C ha i l a k hy a n , m. K. 1 9 36 . Ho r m on a l t h e or y o f p la n t

development. akad Nauk sssR 3: 443-447.

Guns tone , F.D., m.R. Polla rd, C.m. s crimgeour, and H.s.

Veda nayagam . 1977. F att y acids . Pa rt 50. C arbon-13

nuclear magnetic resonance studies of olefinic fatty acids

and esters. Chem Phys Lipids. 18: 115-129.

Hisa mats u, Y., N. Goto, K. Has egawa, and H. s higem ori.

2003. arabidopsides a and B, two new oxylipins from

Arabidopsis thaliana. Tetrahedron Lett. 44: 5553-5556.

miersch, O., R. Kramell, B. Parthier, and C. Wasternack. 1999.

s tructure-ac tivity rel ations of subs titut ed, delet ed or

stereospecifically altered jasmonic acid in gene expression

of barley leaves. Phytochemistry 50: 353-361.

morimoto, T., a. Nagats u, N. murakami, J. s akakibara, H.

Tokuda, H. Nishino, and a. iwashima. 1995. antitumor-

prom ot in g gl yc ero glyc ol ipi ds fr om the gre en al ga ,

Chlorella vulgaris. Phytochemistry 40: 1433-1437.

son, B.W., Y.J. Cho, J.s. Choi, W.K. Lee, D.s. Kim, H.D. Choi,

J.s. Choi, J.H. Jung, K.s. im, and W.C. Choi. 2001. New

galactolipids from the marine bacillariophycean microalga

Nitzschia sp. Nat Prod Lett. 15: 299-306.

s te lm ach, B .a., a. mulle r, P. He nning , s. Ge bhardt , m.

S ch ubert-Z si lave cz , a nd E.W. Wei ler. 2001. A nove l

class of oxylipins, sn1-O-(12-oxophytodienoyl)-sn2-O-

(hexadecatrie noyl)-monogala ctosyl diglyc eride, from

Arabidopsis thaliana. J. Biol. Chem. 276: 12832-12838.

Suzuki, M., S. Yamaguchi, T. Iida, I. Hashimoto, H. Teranishi,

M. Mizoguchi, F. Yano, Y. Todoroki, N. Watanabe, and

M. Yokoyama. 2003. Endogenous α-ketol linolenic acid

levels in short day-induced cotyledons are closely related

to flower induction in Pharbitis nil. Plant Cell Physiol. 44:

35-43.

Takimoto, a., s . Kaihara, and m. Yokoyam a. 1994. stress -

induced factors involved in flower formation of Lemna.

Hsiol Plant. 92: 624-628.

Vick, B. and D. Zimmerman. 1984. Biosynthesis of jasmonic

acid by several plant species. Plant Physiol. 75: 458-461.

Weber, H., B. Vick, and E.E. Farmer. 1997. Dinor-oxo-

pyt odie noic ac id: a ne w he xade ca noid si gna l in the

jasmonate family. Proc. Natl. acad. sci. usa 94 :

10473-10478.

Yamaguchi, s., m. Yokoyama, T. iida, m. Okai, O. Tanaka,

and A. Takimoto. 2001. Identification of a component that

induces flowering of Lemna among the reaction products of

α-ketol linolenic acid (FIF) and norepinephrine. Plant Cell

Physiol. 42: 1201-1209.

Yokoyam a, m., s. Yamaguchi, s. inom ata, K. Komats u, s .

Yoshida, T. iida, Y. Yokokawa, m. Yamaguchi, s. Kaihara,

and a. Takimoto. 2000. s tress -induced factor involved

in flower formation of Lemna is an α-ketol derivative of

linolenic acid. Plant Cell Physiol. 41: 110-113.

50

Botanical Studies, Vol. 47, 2006

一種糖脂涉及阿拉伯芥之花芽形成

Yosuke HisamaTsu

1

, Nobuharu GOTO

2

, Koji HasEGaWa

1

, and Hideyuki

sHiGEmORi

1

1

Graduate school of Life and Environmental sciences,

university of Tsukuba, Tsukuba 305-8572, Japan

2

Department of Biology, miyagi university of Education,

sendai 980-0845, Japan

我們追尋阿拉伯芥 (Arabidopsis thaliana) 涉及花芽形成之生理活性物½。比較花芽形成- 及未發芽

形成- 之發育階段的抽取液於 HPLC 檢測時發現前者有下降之若干.值。化合物 1，此乃減少最明顯之

.值，係單離自阿拉伯芥之地上部。從核磁共振儀及½譜儀之數據得知化合物 1 乃單半乳糖-雙酸甘油

(mGDG)。當阿拉伯芥暴露於長日照只一天時，添加化合物1 可誘導花芽形成。這些結果顯示：化合物

1 可能為花芽形成物½之前驅體或基½，因此乃阿拉伯芥花芽形成之一重要成份。

關鍵詞：花芽形成；阿拉伯芥；短日照；長日照；單半乳糖-雙酸甘油；生理活性物½。