3.3 Differentially expressed genes (DEGs) and differentially
co-expressed genes (DCGs)
The DEGs between drought treatments vs control showed region-specific
and treatment-difference (Fig. 4). The number of DEGs between heavy
drought treatment vs control was greater than that between light drought
treatment vs control (Fig. 4). In addition, the differentially
co-expressed genes (DCGs) within these three regions were 19 (0.72%)
between light drought treatment vs control (Fig. 4a), with 9 being
up-regulated and 10 being down-regulated (Table S1); and was 845
(9.98%) between heavy drought treatment vs control (Fig. 4b), with 592
being up-regulated and 253 being down-regulated (Table S2). Therefore,
in this study, we further analyzed the responses of individuals to heavy
drought treatment based on DEGs and DCGs.
By KEGG functional enrichment analysis on DEGs, gene expressions were
mainly enriched in the pathways of photosynthesis-antenna proteins (with
24 genes up-regulated), cyanoamino acid metabolism (with 13 genes
up-regulated and 12 genes down-regulated) and photosynthesis (with 28
genes up-regulated and 1 genes down-regulated) for individuals from the
eastern region (Fig. 5a; Table S3); enriched in the pathways of one
carbon pool by folate (with 7 genes up-regulated and 2 genes
down-regulated), cyanoamino acid metabolism (with 9 genes up-regulated
and 5 genes down-regulated) and carbon fixation in photosynthetic
organisms (with 27 genes up-regulated) for individuals from middle
region (Fig. 5b; Table S4); and enriched in the pathways of flavonoid
biosynthesis (with 7 genes up-regulated and 3 genes down-regulated),
galactose metabolism (with 25 genes up-regulated and 7 genes
down-regulated) and glycolysis / gluconeogenesis (with 39 genes
up-regulated and 13 genes down-regulated) for individuals from the
western region (Fig. 5c; Table S5). No significant pathway of DEGs
between light drought treatment vs control was enriched in individuals
from the middle and western regions.
By KEGG functional annotation analysis on 845 DCGs, biochemical
metabolic pathways of the first category were identified: metabolism,
genetic information processing, environmental information processing,
cellular processes, and organismal systems. The pathways of second
category were enriched, such as carbohydrate metabolism, amino acid
metabolism, and lipid metabolism (Fig. 6). Among them, a large number of
genes were enriched in the pathways whose descriptions were glycolysis /
gluconeogenesis (with 18 genes up-regulated and 2 genes down-regulated),
starch and sucrose metabolism (with 13 genes up-regulated and 3 genes
down-regulated), MAPK signaling pathway - plant (with 7 genes
up-regulated and 4 genes down-regulated) and plant hormone signal
transduction (with 7 genes up-regulated and 3 genes down-regulated)
(Table S6 & S7).