Sainsbury's commercial director Michael Coupe has taken a big chunk of shares ahead of the supermarket operator's trading statement tomorrow.He took 8,621 shares at 390.53 a time, spending nearly £34,000, and now has 798,285. News of the purchase, which was made last week, comes as data from market research group Kantar Worldpanel shows that Sainsbury's upped its market share in the grocery trade to 16.6% in the 12 weeks to 26 December from 16.3% in the same period the previous year.Morrisons set the benchmark for the supermarket sector on Monday with a better than expected 1% growth in like for like (LFL) sales, excluding petrol and VAT, in the six weeks to 2 January. With fuel included LFL sales were up 4%.Deutsche Bank thinks Sainsbury's numbers will "compare favourably against the shorter-term six-week trading numbers issued by Wm Morrison and Tesco," due in part to the chain's strength in areas not overly affected by the recent spell of bad weather.Coupe, who was appointed in July, is responsible for J Sainsbury's trading, marketing, IT and online operations. He has previously worked for rival supermarkets ASDA and Tesco.Top Director BuysSainsbury (J) (SBRY) Director name: Mr Michael Andrew CoupeAmount purchased: 8,621 @ 390.53p Value: £33,668Top Director SellsIFG Group (IFP) Director name: Mr Mark BogardAmount sold: 500,000 @ 105.88p Value: £529,400Immunodiagnostic Systems Holdings (IDH) Director name: Mr Paul HailesAmount sold: 15,000 @ 940.00p Value: £141,000Anglo Asian Mining (AAZ) Director name: Mr Richard RoundAmount sold: 60,000 @ 78.50p Value: £47,100