Pinduoduo’s founder stepped down suddenly this week, shaking investors who had watched him take the Chinese e-commerce company from nothing to a potential Alibaba competitor in less than a decade.

Colin Huang’s decision to resign as chairman wasn’t a complete surprise. The 41-year-old entrepreneur already quit as CEO last summer, and was expected to eventually leave leadership at Pinduoduo altogether.

But his exit still came faster than expected, and during an uncertain time for many of China’s internet firms as Beijing works to rein in the sector.

Huang will explore “new, long-term opportunities”, the company said in a statement on Wednesday, as it released figures stating it was now China’s largest e-commerce firm.

Shares in Pinduoduo, valued at close to $200bn (£143bn), fell by nearly 8% following the news, wiping about $4bn from Mr Huang’s wealth.

The former Google employee was briefly ranked the second-richest person in China last year, following a surge in sales at his e-commerce business.

Pinduoduo’s 788m active buyers in 2020 overtook Jack Ma’s Alibaba’s 779m annual shopper count for the first time.

Its novel features include team buying, where customers come together to purchase more units at a lower price. They can also play games on the site and are sometimes rewarded with gifts.

lphabet Inc’s YouTube is rolling out a short-form video-streaming service on its platform in the United States as it looks to better compete with rival TikTok in the hugely popular category.

The service, Shorts, let users record mobile friendly vertical videos that can be spiced up with special effects and soundtracks pulled from a music library.

“Starting today and over the next several weeks, we’ll gradually expand our Shorts beta to the U.S.,” YouTube said in a blogpost on Thursday, adding it would weave in newer features on the service like the ability to add text at specific points of the video.

YouTube had rolled out the feature in India in September last year, after TikTok was banned in one of its biggest markets. Shorts currently records more than 6.5 billion daily views globally, YouTube said.

The U.S. Commerce Department said on Wednesday that it has served subpoenas on multiple Chinese companies that provide information and communications technology services in the United States to see if they pose a national security risk.

“Beijing has engaged in conduct that blunts our technological edge and threatens our alliances,” Commerce Secretary Gina Raimondo said in statement.

The subpoenas will gather information to “allow us to make a determination for possible action that best protects the security of American companies, American workers, and U.S. national security.”

In response, China urged the United States to “stop overstretching the concept of national security to politicize economic issues,” foreign ministry spokesman Zhao Lijian told a news briefing on Thursday, adding that China will take measures to safeguard the rights and interests of Chinese companies.

The U.S. statement did not name any companies. China’s Huawei Technologies and ZTE Corp were targeted by the previous administration of Donald Trump for removal from the U.S. telecoms infrastructure.

President Joe Biden’s administration said last month it plans to allow a Trump-era rule targeting Chinese technology firms deemed a threat to the United States to go into effect despite objections from U.S. businesses.

The Commerce Department issued an interim final rule in the final days of the Trump administration aimed at addressing information and communications technology supply chain concerns and said it would become effective after a 60-day period of public comment.

Last month, the department said it would continue to accept public comment on the rule until March 22, when it would go into effect. The subpoenas would not have an impact on the interim final rule’s timing, a department official said on Wednesday.

The U.S. Chamber of Commerce and groups representing major industries raised concerns in a letter to the Commerce Department in January that the interim rule gave the government “nearly unlimited authority to intervene in virtually any commercial transaction between U.S. companies and their foreign counterparts that involves technology.”

Business Roundtable, a group representing major U.S. chief executives, said earlier the proposal is “unworkable for U.S. businesses in its current form.”