[Seminar] The functions of WHIRLY1 functions in stress and senescence

Seminar

Title: The functions of WHIRLY1 functions in stress and senescence

Speaker: Christine H. Foyer

Affiliation: Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK

The WHIRLY family of ssDNA binding proteins form tetramers and larger oligomeric structures in chloroplasts and mitochondria.

Chloroplasts are major sensors of environmental change, particularly stress perception. Plants growing in fluctuating environments require coordinated regulation of photosynthesis, growth and defence. WHIRLY1 is a member of the WHIRLY family of single-stranded DNA-binding proteins that is found in both plastids and the nucleus. In the nucleus WHIRLY1 acts as a transcription activator for pathogen-related gene expression and as a repressor for the kinesin-like protein 1 that modulates telomere length. In chloroplasts, WHIRLY1 is required for plastid genome stability and plastid gene transcription. However, much remains uncertain concerning how WHIRLY1 participates in the regulation of leaf development and stress tolerance. We have characterised WHIRLY1 functions in barley using RNAi-knockdown lines (W1-1, W1-7 and W1-9) that have very low levels of HvWHIRLY1 transcripts that were provided by Dr Karin Kuprinska (Kiel). The WHIRLY1-deficient plants were phenotypically similar to the wild type but in early generations produced fewer tillers. Photosynthesis rates were similar in all lines but W1-1, W1-7 and W1-9 leaves had significantly more chlorophyll and less sucrose than the wild type. Transcripts encoding specific sub-sets of chloroplast-localised proteins such as ribosomal proteins, subunits of the RNA polymerase and the thylakoid NADH and cytochrome b₆/f complexes were much more abundant in the W1-7 leaves than the wild type. While susceptibility of aphid infestation was similar in all lines, the WHIRLY1-deficient plants showed altered responses to drought and to nitrogen deficiency, maintaining higher photosynthetic CO₂ assimilation rates than the wild type under stress conditions. We propose that WHIRLY1 has important functions in stress tolerance.