Scientists from DuPont Pioneer used gene-silencing approach to modulate the
levels of ethylene biosynthesis in corn and study its effect on grain yield
under drought conditions in the field. The results of the study were
released in Plant Biotechnology Journal.

Commercially relevant transgenic events were created with down-regulated ACC
syntheses (ACSs), enzymes that catalyze the rate-limiting step in ethylene
biosynthesis. These events exhibit decreased release of ethylene to
approximately half compared with non-transgenic nulls. Field tests of the
transgenic hybrids and controls were conducted in drought-stress and
rain-fed areas in the U.S.

Results of yield data showed that transgenic events had significantly
increased grain yield compared with the controls, with the best event having
a 0.58 Mg/ha (9.3 bushel/acre) increase after a flowering period drought
stress. Furthermore, secondary traits analysis showed that there was a
consistent decrease in the anthesis-silking interval and a concomitant
increase in kernel number/ear in transgene-positive events versus controls.
Selected events were also field tested under a low-nitrogen treatment, and
the best event was found to have a significant 0.44 Mg/ha (7.1 bushel/acre)
yield increase.

Based on the results, it was concluded that down-regulating the ethylene
biosynthetic pathway can improve the grain yield of maize under abiotic
stress conditions.

[www.ncbi.nlm.nih.gov]