Expression levels of two gene pairs in the same pathway (A) AT4G27550 and AT4G39770, and (B) AT2G45560 and AT3G11180 with some samples color coded according to their tissue types or treatments: shoot_salt, shoot tissues under salt stress; stele_protoph_salt, stele and protophloem cells under salt stress; columell_root, columella root cap under salt stress, low pH, and sulfur deficiency; whole_root_salt, whole root under salt stress; whole_root_pH, whole root under low pH; root_low_pH, other root cells under low pH.