Proteins Produced during Salt Stress in Tobacco Cell Culture

The protein pattern of cultured tobacco (Nicotiana tabacum L. var Wisconsin 38) cells that have become adapted to a medium containing 10 grams NaCl per liter was compared to that of unadapted cells on one-dimensional sodium dodecyl sulfate gels. Two protein bands (32,000 and 20,000 daltons) were much more abundant in the salt-adapted cells, and one protein (26,000 daltons) was unique to the salt cells. This protein pattern did not change during the growth cycle of the cells. When salt-adapted cells are transferred to control medium, their ability to grow in the salt-containing medium returns to that of control cells after one passage in the control medium (Hasegawa, Bressan, Handa 1980 Plant Cell Physiol 21: 1347). Within this time the levels of the 32,000 and 20,000 dalton proteins also return to that of the control cells, but the 26,000 dalton protein does not disappear until after at least two passages in control medium. Amino acid analyses of these three proteins revealed that they all contain some hydroxyproline.