* Nikkei falls to lowest since April 3

* Topix’s 33 subsectors all in the red

* Japan Airlines falls after reports of system glitch

By Ayai Tomisawa

TOKYO, May 8 (Reuters) – Japan’s Nikkei tumbled to a five-week low on Wednesday morning as fears there might be a breakdown in U.S.-China trade negotiations continued to pull down cyclical stocks.

Investors were spooked by a sell-off in Wall Street overnight where its Dow Jones Industrial Average had its second-biggest daily percentage drop of the year.

The Nikkei share average tumbled 1.7 percent to 21,546.57, the lowest since April 3, before ending the morning session down 1.6 percent at 21,584.26.

This followed a 1.5 percent drop on Tuesday, when investors returned to the market after a