Scientists from Anhui Agricultural University in China studied the role of a
differentially expressed gene, PbSPMS, in yellow-green pear Dangshansuli and
its russet-colored mutant Xiusu. The results, published in Plant Cell,
Tissue and Organ Culture, show that the gene improves Arabidopsis'
resistance to drought and salt stress.

The findings indicated that the relative area of the vascular bundles of the
transgenic plants was bigger than that of the wild-type. The secondary
thickened cell wall of xylem was also found to be thicker in the transgenic
plants than the wild-type. Greater contents of polyamine, phenolics, and
suberin were observed in the transgenics than the wild-type.

When exposed to drought and salt stress, PbSPMS introduction caused the fast
buildup of spermidine and spermine in Arabidopsis, in higher contents than
in the wild-type plants. This indicates that PbSPMS contributes to stress
response quickly to decrease the negative effects of stress. It was also
observed that PbSPMS increased the contents of proline, H2O2, peroxidase,
and soluble sugars in the plants. With longer exposure to stress, the
contents of all the compounds increased slowly, and the greater the drought
resistance was observed in transgenic plants.



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