The expression of histone 2A in onion (Allium cepa) during the onset of dormancy, storage and emergence from dormancy

The tissue-specific and developmental expression of histone 2A was studied in onion (Allium cepa 'Robusta'), using northern blots. Histone 2A expressi on was enriched in basal tissues, particularly in the inner, meristematical ly active parts of bulbs. The expression was assessed during a time course of bulb development, dormancy onset and post-harvest sprouting in field-gro wn material. During bulb development histone 2A expression in the inner bul b declined rapidly during bulb ripening, reaching a minimum with the onset of dormancy. During post-harvest storage, expression increased slowly, reac hing a peak in the spring, coinciding with the first observed sprout emerge nce. It was concluded that in onion, as in other plant systems, histone 2A expression is linked to cell division and dormancy level, the peak in expre ssion during post-harvest storage indicating the time of dormancy breakage. In cultivars where post-harvest sprouting occurred much earlier or much la ter than in 'Robusta', this expression peak occurred at about the same time of year, regardless of sprouting time. It was concluded that differences i n storage longevity between cultivars were not due to differing times of do rmancy breakage. Factors controlling the rate of sprout emergence post-dorm ancy are likely to be major determinants of storage capacity.