Figure S1.
Isolation of a pistil extract fraction containing a pollen germination stimulant.
(a) HPLC chromatogram of a partially purified (ethyl acetate-insoluble, methanolsoluble) fraction of an extract prepared from 36 pistils and fractionated on a reversephase C
18
column.
(b) The relevant portion (17-21 minutes) of the chromatogram in (a) is shown.
(c) In vitro pollen germination stimulation by five-minute HPLC fractions of methanolsoluble fraction of the pistil extract (extract) or pollen growth medium (PGM) control.
(d) In vitro pollen germination stimulation by one-minute HPLC fractions of the methanol-soluble fraction of pistil extract (extract) or pollen growth medium (PGM) control.
(c-d) It should be noted that only ~33% of germination activity was recovered after passing the pistil extracts prepared from 36 pistils through the C
18
column; consequently, the positive fraction collected from a C
18
column elicited low level of pollen germination response compared to partially purified extract (methanol-soluble and ethyl acetateinsoluble fraction) from 36 pistils that was not passed through a C
18
column (Figure 1k,l).
Pollen germination percentage shown in (c) and (d) was recorded three hours after depositing pollen on PGM plates and incubating in a 22°C chamber.
Figure S2.
Mass spectrometric (MS) analysis of HPLC fractions of a partially-purified, pistil extract containing a pollen germination stimulant.
(a) The spectrum of bioassay-positive fraction in Enhanced MS scan mode. The ions at m/z 201.8, 223.8, and 240.8 appear only in the bioassay-positive fraction and they correspond to the protonated ([M+H] + ), sodiated ([M+Na] + ), and potassiated ([M+K] + ) molecule, respectively. Peaks that are observed only in this fraction, but not in any other bioassay-negative fraction, are labeled. Y axis - cps, counts per second.
(b) MS scan of a bioassay-negative fraction; 8-9 minutes fraction is shown as a representative of bioassay-negative fractions. In this graph, only most abundant peaks are labeled. Y axis - cps, counts per second.
(c) Liquid chromatography-Mass Spectrometry analysis in Multiple Reaction Monitoring
(MRM) mode of the partially purified pistil extract. MRM transition: 201.8

137.8. Y axis - cps, counts per second.

(d) MS/MS fragmentation pattern of 201.8 Parent ion (arrow) with the most abundant fragment at m/z 137.8 (arrow head). Y axis - cps, counts per second.
Figure S3. ESI FT-ICR analysis of a partially-purified, ethyl acetate-insoluble, methanolsoluble fraction of a pistil extract.
(a) Mass spectra of the buffer control.
(b) Mass spectra of the bioassay-positive fraction.
(c) Mass spectra of the bioassay-negative fraction.
(a-c) The ions at m/z 202.12618, 224.10811, and 240.23232 appear only in the bioassaypositive fraction and they correspond to the protonated ([M+H]
+
), sodiated ([M+Na]
+
), and potassiated ([M+K]
+
) molecule, respectively, with a chemical formula of
C
10
H
19
NSO.
Figure S4. Chemical structures and reactions to synthesize small molecules with a molecular formula of C
10
H
19
NSO.
(a,b) Published compounds with molecular formula of C
10
H
19
NSO and possessing a sulfoxyl S=O bond (Chemla and Ferreira, 2004; Chen et al.
, 2006). Neither molecule is expected to have a mass spectrum containing the [M+H]
+
-64 fragment (= m/z 138 ion) caused by the loss of methanesulfenic acid (CH
3
SOH) and thus are distinct from N methanesulfinyl 1-azadecalin and N -methanesulfinyl 2-azadecalin shown in Figures 2a,c.
(c-f) Schemes of chemical reactions used to synthesize four compounds with a chemical formula of C
10
H
19
NSO. The substrates, reagents, product of the reactions and synthesis conditions (h, hours) for each reaction are indicated. Detailed synthesis protocol for each of the four reactions shown here can be found in Supplementary experimental procedures.
Figure S5.
ESI FT-ICR analysis of 10-(methylsulfinyl)-10-azabicyclo[4.3.1]decane and
3,3-dimethyl-1-(thiomorpholino)butan 1-one.
(a) FT-ICR mass spectrum for 10-(methylsulfinyl)-10-azabicyclo[4.3.1]decane (inset and
Figure S4e). The measured value for [M+H]
+
is 202.12606, which is consistent with the calculated value (202.12601) for a formula C
10
H
20
NSO.

(b) QCID MS/MS fragmentation spectrum for the [M+H]
+
ion of compound 10-
(methylsulfinyl)-10-azabicyclo[4.3.1]decane. The main fragment at m/z 138.12870 is consistent with the loss of CH
3
SOH. Note that this MS/MS spectrum is characterstically different from those of other three compounds shown in Figures 2d,f and Figure S5d; for example, loss of a water molecule (H
2
O ion at m/z 184.11556) observed here was not detected in other three compounds.
(c) FT-ICR mass spectrum for 3,3-dimethyl-1-(thiomorpholino)butan 1-one (inset and
Figure S4f). The measured value for [M+H] + is 202.12623, which is consistent with the calculated value (202.12601) for a formula C
10
H
20
NSO.
(d) QCID MS/MS fragmentation spectrum for the [M+H]
+
ion of compound 3,3dimethyl-1-(thiomorpholino)butan 1-one. The fragment at m/z 104.05286 is consistent with the loss of C
6
H
10
O and the MS/MS pattern shown here is fully consistent with the chemical structure of 3,3-dimethyl-1-(thiomorpholino)butan 1-one. Note that this
MS/MS pattern is characteristically different from those of other three compounds described in Figures. 2d,f and Figure S5b, in that there is no loss of CH
3
SOH from this compound which was observed in all of the other three compounds. Peaks denoted with
(*) are those that originated due to electrical noise from the instrument and are unrelated to 3,3-dimethyl-1-(thiomorpholino)butan 1-one.
Figure S6. Liquid chromatography-Mass Spectrometry analysis of a partially purified pistil extract spiked with Sulfinylated azadecalins.
(a) LC-MS analysis (MRM mode) of partially purified pistil extract spiked with N -
Methanesulfinyl 1-azadecalin. Y axis - cps, counts per second. The m/z 202 ion in pistil extract is marked with an arrow and N -Methanesulfinyl 1-azadecalin is indicated with an arrowhead.
(b) LC-MS analysis (MRM mode) of partially purified pistil extract spiked with N -
Methanesulfinyl 2-azadecalin. Y axis - cps, counts per second. The m/z 202 ion in pistil extract is marked with an arrow and N -Methanesulfinyl 2-azadecalin is indicated with an arrowhead.

Movie S1. Stimulation of pollen (Columbia accession) germination by sulfinylated azadecalins.
Time-lapse imaging of Arabidopsis pollen (Columbia accession) germination on a solid pollen growth medium. Pollen grains from the same anther were spotted proximal to three holes, one filled with 50

M NMethanesulfinyl 1-azadecalin, a second one filled with 50

M NMethanesulfinyl 2-azadecalin and a third one filled with liquid PGM
(control). The pollen growth medium was prepared as described in (Li et al.
, 1999). Time elapsed between two frames in each movie–two minutes (00:02hrs)–is indicated on the top left hand corner and the scale bar (100
 m) is shown on the bottom right corner of each frame.
Movie S2. Stimulation of pollen (Landsberg accession) germination by sulfinylated azadecalins.
Time-lapse imaging of Arabidopsis pollen (Landsberg accession) germination on a solid pollen growth medium. Pollen grains from the same anther were spotted proximal to three holes, one filled with 50

M NMethanesulfinyl 1-azadecalin, a second one filled with 50

M NMethanesulfinyl 2-azadecalin and a third one filled with liquid PGM
(control). The PGM was prepared as described in (Li et al.
, 1999). Time elapsed between two frames in each movie–20 minutes (00:20hrs)–is indicated on the top left hand corner and the scale bar (100
 m) is shown on the bottom right corner of each frame.
Methods S1.
Supplementary experimental procedures: exudate treatments; liquid chromatography; low-resolution mass spectrometric analysis; molecular weight determination and MS/MS analysis using FT-ICR; and synthesis of four compounds with a chemical formula of C
10
H
19
NSO ( N -methanesulfinyl 1-azadecalin, N -methanesulfinyl
2-azadecalin, 10-(methylsulfinyl)-10-azabicyclo[4.3.1]decane, and 3,3-dimethyl-1-
(thiomorpholino)butan-1-one).