3.2.3. KEGG pathway analysis
The number of DEMs enriched in
the biosynthesis pathway of flavonoids and amino acids ranked the top
five among KEGG pathways (Figure 4). The expressions of L-proline,
L-lysine, L-isoleucine, S-adenosylmethionine, and L-saccharopine in the
biosynthesis of amino acids were higher in RM than in RL (Figure 5a),
while citrate and L-saccharopine were higher in RH than in RM (Figure
5c). With soil salinity increased (RH vs. RL), three of the four DEMs in
the biosynthesis of amino acids
(L-proline, aspartic acid, and
citrate) were up-regulated (Figure 5b). Among the DEMs involved in
flavonoid biosynthesis, the expressions of (-)-naringenin, vitexin,
(+)-gallocatechin, pinocembrin, (-)-epicatechin and epigallocatechin
were higher in RM vs. RL (Figure 5a) and RH vs. RL (Figure 5b).
3.3. Combined analysis of soil
properties and M. azedarach DEMs
Six soil chemical properties (salinity, Na+,
Cl-, K+, available phosphorus and
available potassium) were correlated negatively with four DEMs ofM. azedarach : prunasin, androstendione,o -succinyl-L-homoserine and traumatic acid (Figure 6). By
contrast, alkaline phosphatase activity was positively correlated with
these four DEMs. Soil pH was negatively correlated with prunasin, and
Ca2+ was positively correlated with prunasin and
corticosterone.