Science - USA (2021-12-03)

andLBD29, stele) (Fig. 2E). However, our
scRNAseq data showed that expression of the
core patterning geneSHRwas specific to the
endodermis and not to the stele (Fig. 2E),
where theArabidopsisortholog is expressed ( 9 ).
All three maize paralogs ofSHR(designated
ZmSHR1,ZmSHR2, andZmSHR2-h) showed
the same endodermal enrichment in the pro-
files generated by DPL and single-cell analysis

(Fig. 3, A and B). We speculated that the ex-

pression of this mobile, division-inducing tran-

scription factor adjacent to the cortex could be

related to a role in the expansion of that tissue.

Mobile SHR regulates cortical complexity in

maize andSetaria

To confirm SHR transcript localization, we per-

formed in situ hybridization on all threeSHR

mRNAs, confirming their localization in the

endodermis (Fig. 3, C to E, and fig. S7, A to I). A

1.4-kb upstream and downstream transcription-

al reporter forZmSHR2also showed signal in

the root endodermis, in agreement with our dye-

sorted and single-cell profiles (Fig. 3D). No sig-

nal was found in the stele, confirming thatSHR2

transcript localizes to different cell types in

maize compared withArabidopsis. Consistently,

1250 3 DECEMBER 2021¥VOL 374 ISSUE 6572 science.orgSCIENCE

AB

C D

E F

ZmSHR2

ZmSHR1

ZmSHR2-h

SHR2 SHR1 SHR2-h

St En Co Ep

ZmSHR2::RFP

ZmSCR1

Expression Level

(counts)

QC Columella SteleEndodermis Cortex Epidermis

250

500

750

ZmSHR2-h

ZmSHR2

ZmSHR1

0 1 2 3 4 5 6 7 8 91011121314151617181920

Clusters

Average Expression Percent Expressed

-1 012

1.5 3.0

En

G H

St En Co Ep

ZmSCR1::SCR1-GFP

ZmSHR1::SHR1-YFP

St Co Ep

Fig. 3. SHR and SCR expression in maize endodermis and differences
between transcriptional and translational reporters.(A) Expression of the
threeZmSHRparalogs (SHR1,2,2-h) from sorted cells. Error bars are SDs.
(B) Dot plots representing scRNAseq analysis showing expression ofZmSHR
paralogs in endodermis and, at a low level, stele. (C)ZmSHR2-hin situ
hybridization showing endodermal expression. (D)ZmSHR2in situ hybridization

and transcriptional RFP reporter. (E) In situ hybridization ofZmSHR1.

(F) Translational YFP reporter forZmSHR1 with inset showing protein in cortex

layers. (G) In situ hybridization ofZmSCR1.(H) Translational reporter

SCR1-GFP reporter showing protein in the stele. Scale bars, 50mm[(F)and

(H)] and 100mm [(C), (D), (E), and (G)]. Cyan in confocal images [(D), (F),

(H)] is autofluorescence at an excitation wavelength of 405 nm.

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