Numbers stack up for stressed tomatoes
I often tell my students that they can work out what an enzyme
does from its name. However, when it comes to structural and regulatory
proteins this simple idea may not always work. For example, a family of
regulatory phosphoserine binding proteins are known as 14-3-3 proteins: the
name comes from the numbers of particular structural domains in each molecule.
They are already known to be involved in the regulation of many cellular
activities, probably including stress responses. It is this topic that has been
the subject of study by Xu and Shi (Nanjing and Beijing,
pp. 965–974). The authors have firstly identified the members of the gene
family encoding 14-3-3 proteins in tomato (Solanum
lycopersicum). There are 12 genes in all, falling into two major groups.
They have then subjected young plants to three different stresses: salt stress (exposure
to 100 mm NaCl), potassium
deficiency and iron deficiency. Expression levels in roots of the 12 genes were
then determined by quantification by real-time RT–PCR of the mRNA
concentrations before and after the application of the stresses. The authors
point out the advantages of this technique for studying expression of several
genes simultaneously, especially if any of the genes are expressed at low
level, a point with which those of us who use this technique will readily
agree. Their analysis showed that the 12 genes were expressed at very different
levels in control roots: mRNA concentrations ranged from ‘not detectable’ to ‘high’.
There were also differential responses to the stresses: eight of the genes were
upregulated in response to K deficiency, one in response to Fe deficiency and
four in response to salt stress. Only one gene, TFT7, was upregulated
under all three stresses. These data support the view that 14-3-3 proteins are
involved in stress responses and raise the possibility of cross-talk between
signalling pathways involved in responses to widely differing stresses.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
