Question

Role of total soluble sugar in plant defence to insect

Answer 1

HEY MATE!!

Jasmonates regulate plant secondary metabolism and herbivore resistance. How they influ-

ence primary metabolites and how this may affect herbivore growth and performance are not

well understood.

We profiled sugars and starch of jasmonate biosynthesis-deficient and jasmonate-insensi-

tive

Nicotiana attenuata

plants and manipulated leaf carbohydrates through genetic engi-

neering  and

in vitro

complementation  to  assess  how  jasmonate-dependent  sugar

accumulation affects the growth of

Manduca sexta

caterpillars.

We found that jasmonates reduce the constitutive and herbivore-induced concentration of

glucose and fructose in the leaves across different developmental stages. Diurnal, jasmonate-

dependent inhibition of invertase activity was identified as a likely mechanism for this phe-

nomenon. Contrary to our expectation, both

in planta

and

in vitro

approaches showed that

the lower sugar concentrations led to increased

M. sexta

growth. As a consequence, jasmo-

nate-dependent depletion of sugars rendered

N. attenuata

plants more susceptible to

M. sexta

attack.

In conclusion, jasmonates are important regulators of leaf carbohydrate accumulation and

this determines herbivore growth. Jasmonate-dependent resistance is reduced rather than

enhanced through the suppression of glucose and fructose concentrations, which may con-

tribute to the evolution of divergent resistance strategies of plants in nature.