OCCURRENCE OF HSP70 FRAGMENTS IN SEVERAL DEVELOPMENTAL STAGES OF ARABIDOPSIS-THALIANA

Extracts of seeds, leaves, flowers, and green (unripe) and yellow (rip e) fruits of Arabidopsis thaliana were investigated with anti-HSP70 an tisera and affinity chromatography on ATP-agarose. Besides HSP70, a ba nd sized about 35 kDa was found in fruits and seeds but not in other t issues. This band reacts strongly with an antiserum that is directed a gainst a C-terminal HSP70 sequence. This 35 kDa band is not bound to A TP-agarose. Elution of the ATP-agarose with ATP resulted only in the H SP70 protein (apparent size 65 kDa), which occurs in about equal amoun ts in all organs. Subsequent elution with urea resulted in a 75 kDa pr otein reacting with an anti-HSP70 antiserum. This <<HSP75>> occurs mai nly in flowers and green fruit. Only trace amounts of this protein wer e found in ripe fruits and seeds: N-terminal fragments (50 kDa and 35 kDa) are found in these organs instead. The role of the C-terminal 35 kDa fragment occurring in fruits and seeds is discussed.