Abstract
Plant terpene
synthases (TPSs) are key enzymes responsible for terpene biosynthesis, and can
play important roles in defense against herbivore attack. In rice, the protein
sequence of TPS46 was most closely related to maize TPS10. However, unlike maize
tps10, tps46 was also constitutively expressed in rice even in the absence of
herbivore attack. Potential roles or constitutive emissions of specific
volatiles may due to the constitutive expressions of tps46 in rice. Therefore,
in the present study, RNA interference (Ri) and overexpression (Oe) rice lines
were generated to investigate the potential function of TPS46 in Oryza sativa
sp. japonica. Interestingly, the rice plants become more susceptible to
Rhopalosiphum padi when expression of tps46 was silenced compared with Wt in
greenhouse conditions. Artificial infestation bioassays further confirmed that
Ri rice lines were susceptible to R. padi, whereas Oe rice lines were repellent
to R. padi. Based on GC-MS and ToF-MS analysis, a total of eight volatile
products catalyzed by TPS46 in rice were identified. Among them, only limonene
and Ebf could be detected in all the Ri, Oe, and Wt lines, whereas other six
volatiles were only found in the blend of volatiles from Oe lines. Moreover, the
amount of constitutive limonene and Ebf in the Ri lines was significantly lower
than in Wt lines, while the amounts of these two volatiles in the Oe line were
obviously higher than in control rice. Our data suggested that the constitutive
emissions of Ebf and limonene regulated by the constitutive expression of tps46
may play a crucial role in rice defense against R. padi.
Consequently, tps46
could be a potential target gene to be employed for improving the resistance of
plants to aphids.