Variation in the amount of Hsp70 among different floral organs in three alternative color phenotypes of Iris pumila

Abstract

The 70kD heat shock proteins (Hsp70s) are highly conserved molecular chaperones that playessential roles in numerous cellular processes, including the folding of newly synthesized andstress-denatured proteins, the translocation of proteins across membranes, as well as the degradation of aggregated proteins. Here we examined the variation in the abundance of Hsp70s indifferent floral organs of the three distinctive color morphs in Iris pumila. Flowers of twenty sevengenotypes raised in a common-garden and belonging to three colour classes: yellow, dark blueand dark violet, were collected (9 per each class) for an immunoblot analysis. The content of Hsp70was quantifed in four floral organs: falls, standards, stamens and style arms. The immunoblot analysis revealed that the expression of Hsp70s was floral organ-specifc. While only one Hsp70 isoformwas expressed in the standards and falls, the stamens and style arms expressed two isoforms. Therelative abundance of Hsp70 varied among differed flower organs as well. The lowest value wasrecorded in the standards and the highest in the stamens, whereas its abundance in the falls andstyle arms appeared to be intermediate. Such variation pattern was detected exclusively in thedark violet colour morphs. In the yellow flowers, however, the amount of Hsp70 tended to be lower compared to the dark blue or dark violet colour morphs. This study provides original evidencefor organ-specifc Hsp70 expression in flowers of I. pumila plants, likely due to the differential metabolic activities occurring in the cells of these functionally distinctive floral structures.