Differential expression and evolutionary analysis of the three ferritin genes in the legume plant <i>Lupinus luteus</i>

Abstract

We identified three genes coding for ferritins in the legume plant – yellow lupine ( LlFer1 , LlFer2 , LlFer3 ). Proteins coded by these genes have a typical ‘plant’ structure, and precursors of their functional subunits are probably targeted to plastids. Despite very high amino acid sequence identity of mature polypeptides (86–90%), their genes are differentially induced by iron and the ‘stress‐related’ hormone abscisic acid (ABA). In tissues of lupine plants grown in hydroponics, the transcription of all three classes was induced by both iron and ABA with different kinetics. However, in homogenous lupine cell suspension, the accumulation of all classes of ferritin messages was also induced with iron, whereas only one gene ( LlFer2 class) was transcribed in response to ABA. Moreover, the activity of LlFer3 gene was repressed by ABA, but up‐regulated by light. During the development of symbiotic interactions of lupine plants with the bacteria Bradyrhizobium lupini , only two out of three ferritin genes were active – LlFer2 and LlFer3 . Increased accumulation of ferritin RNAs and polypeptide(s) correlated with late developmental stages of root nodules, suggesting the involvement of two types of ferritin subunits in the protection against senescence‐related iron release. The phylogenetic analysis of ferritin amino acid sequences is in agreement with classical systematics. However, because of clear grouping of some legume ferritins outside all other legume sequences, a possibility of a more diverse character of ferritins in this family should also be considered.