Figure legends
Figure 1 Photoperiod and spectral distribution of three light
regimens. (a) Schematic representation of photoperiod and light
spectral quality in SW, LW, and LR treatment. The white and bright red
boxes at the top represented the duration of ~320 µmol
m−2 s−1 illumination (12h), the gray
and pink boxes represented the duration of ~12 µmol
m−2 s−1 illumination (10h), and the
black box represented the duration of darkness (12h or 2h). (b) A real
view of the light environment for wheat plants provided by LED lamps in
SW, LW, and LR treatment. SW, short photoperiod + white LEDs; LW, long
photoperiod + white LEDs; LR, long photoperiod + red LEDs.
Figure 2 LR treatment accelerated flowering and increased the
number of fertile florets per spike (NFFs) at flowering. (a)
Representative graph depicting the development stages of wheat under
three light regimens. (b) The number of fertile florets per spike at
flowering. (c) The number of spikelets per spike at flowering. (d) The
morphological changes of floret primordia (x axis, days after
terminal spikelet stage). The letter + number on floret primordia
represented primordia from the most proximal (F1) to the most distal
(F11) with respect to the spike rachis. The dynamics of the number of
total floret primordia (e), fertile floret primordia (f), and infertile
floret primordia (g). Significant differences between treatments were
indicated by asterisks (LSD test, *P < 0.05, ns, not
significant, black and red asterisks represented the differences between
LW versus SW and LR versus LW, respectively). Bars
represented standard error (n = 6).
Figure 3 Effect of three light regimens on assimilate
accumulation in wheat. (a) Dry plant weight. (b) Dry spike weight. (c)
Dry matter partitioning to spike. (d) Soluble sugar content in the
spike. (e) Glucose content in the spike. (f) Fructose content in the
spike. Significant differences between treatments were indicated by
asterisks (LSD test, *P < 0.05, black and red asterisks
represented the differences between LW versus SW and LRversus LW, respectively). Bars represented standard error (n = 6
in a, b, and c; n = 3 in d, e, and f).
Figure 4 Samples collection and gene expression dynamics under
three light regimens. (a) RNA-seq samples collected at an interval of
six days (3-15) or three days (15-27) from the terminal spikelet stage
(TS) to flowering stage (FS) in SW, LW, and LR treatment. Principal
component analysis (PCA, b) and hierarchical clustering (c) of RNA-seq
data showed distinct stages of floret primordia development in SW, LW,
and LR treatment. Numbers represented sampling time and biological
replicate. (d) Representative images of the floret primordium at
distinct development stages. (e) A cluster dendrogram of all
transcriptomes reflecting the similarity of gene expression in different
light regimens.
Figure 5 Regulatory network of key genes/homologs involved in
long photoperiod-accelerated flowering. (a) The number of
differentially expressed genes (DEGs) during floret development. (b) A
Venn diagram showing the number of DEGs specifically expressed at
different sampling times. (c) A heat map of key genes/homologs involved
in the photoperiodic flowering pathway. Colors represented
log2FC in expression levels of LW relative to SW. The
star represented a significant level (absolute log2FC ≥
1, FDR-adjusted P < 0.05). (d) The protein-protein
interaction (PPI) analysis between key genes/homologs and functional
DEGs. Node color represented that the gene displayed significantly
different expression in Stage I (yellow), Stage II (green), 21 DAT
(i.e., Stage III in SW and Stage IV in LW) (blue), and Stage IV (red),
respectively. Node shape represented that the gene displayed functional
categories, including light response (square), hormone metabolism
(triangle), carbohydrate metabolism (diamond), flower development
(circular), and more than one of the four functions (hexagon). The genes
in the red and blue dotted boxes were up- and down-regulated,
respectively, in LW compared to SW. (e) GO terms were significantly
enriched in functional DEGs that interact directly with CO -like
genes. (f) GO terms were significantly enriched in functional DEGs that
interact directly with HD3A gene.
Figure 6 Transcriptional signatures of LR versus LW
reflected flowering acceleration and NFFs increase. (a) The number of
DEGs during floret development. (b) A Venn diagram showing the number of
DEGs specifically expressed at different sampling times. (c) The optimal
number of clusters according to the k -means function in R
software. (d) Heat maps of coexpression clusters for 12382 DEGs. Colors
represented log2FC in expression levels of LR relative
to LW. (e) The mean expression level across all genes and Go terms
enriched significantly in different coexpression modules.
Figure 7 Regulatory network for LR-mediated “early flowering”
and “high yielding”. The development of all floret primordia in a
wheat spike included four distinct stages: differentiation (Stage I),
differentiation and morphology development concurrently (Stage II),
morphology development (Stage III), and polarization (Stage IV).
Compared to SW, LW treatment accelerated flowering by increasing
assimilate availability moderately, advancing Stage IV initiation, and
shortening the developmental time in Stage III, in which theGI -CO -like-HD3A framework played a central role;
however, we could not afford to ignore the loss of fertile florets
caused by LW treatment. Surprisingly, wheat plants treated with LR
treatment flowered early and had high NFFs. LR treatment accelerated the
differentiation rate of floret primordia in Stage I, shortened the time
required in Stage II, enhanced assimilate availability and morphological
development of floret primordia highly in Stage III, and maintained the
continuous development of fertile floret primordia in Stage IV until
flowering. A dynamic gene network centered on ubiquitin, calcium
signaling, ALDH s, ZF s, and HSP s was predicted to
play an important role in “early flowering” and “high yielding” in
LR treatment.