Previous studies have indicated that plant plastocyanins are involved in
copper homeostasis. However, their physiological relevance remains elusive.
The team of Xin-Tong Zhou of Chinese Academy of Sciences found that a
plastocyanin gene, SsPETE2, from seepweed (Suaeda salsa) has a novel
antioxidant function, which was associated with its copper-chelating
activity.

In S. salsa, the expression of SsPETE2 increased when the plant was exposed
to oxidative stress. When SsPETE2 was expressed in Arabidopsis, it enhanced
the antioxidant ability of the transgenic plants. The SsPETE2 protein binds
to Cu ions and alleviate formation of hydroxyl radicals. Thus, SsPETE2
expression lowers the free Cu content that was associated with plants under
oxidative stress.

Interestingly, SsPETE2-expressing plants exhibited more potent tolerance to
oxidative stress than plants overexpressing AtPETEs. This means that the
SsPETE2 protein has a stronger copper-binding activity than AtPETEs protein.

These results demonstrate that plant PETEs play a role in oxidative stress
tolerance by regulating Cu ions in plants under stress conditions. SsPETE2,
an efficient copper-chelating PETE, could be potentially used in crop
genetic engineering.



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