ST_LineFromText

CREATE TABLE gis_line  (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
    (LineFromText('LINESTRING(0 0,0 10,10 0)')),
    (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')),
    (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10)))));