Molecular evolution and transcriptional regulation of the oilseed rape proline dehydrogenase genes suggest distinct roles of proline catabolism during development

Abstract

Six BnaProDH1 and two BnaProDH2 genes were identified in Brassica napus genome. The BnaProDH1 genes are mainly expressed in pollen and roots' organs while BnaProDH2 gene expression is associated with leaf vascular tissues at senescence. Proline dehydrogenase (ProDH) catalyzes the first step in the catabolism of proline. The ProDH gene family in oilseed rape (Brassica napus) was characterized and compared to other Brassicaceae ProDH sequences to establish the phylogenetic relationships between genes. Six BnaProDH1 genes and two BnaProDH2 genes were identified in the B. napus genome. Expression of the three paralogous pairs of BnaProDH1 genes and the two homoeologous BnaProDH2 genes was measured by real-time quantitative RT-PCR in plants at vegetative and reproductive stages. The BnaProDH2 genes are specifically expressed in vasculature in an age-dependent manner, while BnaProDH1 genes are strongly expressed in pollen grains and roots. Compared to the abundant expression of BnaProDH1, the overall expression of BnaProDH2 is low except in roots and senescent leaves. The BnaProDH1 paralogs showed different levels of expression with BnaA&C.ProDH1.a the most strongly expressed and BnaA&C.ProDH1.c the least. The promoters of two BnaProDH1 and two BnaProDH2 genes were fused with uidA reporter gene (GUS) to characterize organ and tissue expression profiles in transformed B. napus plants. The transformants with promoters from different genes showed contrasting patterns of GUS activity, which corresponded to the spatial expression of their respective transcripts. ProDHs probably have non-redundant functions in different organs and at different phenological stages. In terms of molecular evolution, all BnaProDH sequences appear to have undergone strong purifying selection and some copies are becoming subfunctionalized. This detailed description of oilseed rape ProDH genes provides new elements to investigate the function of proline metabolism in plant development.

Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence

“…The degradation of Pro (Fig. 6, pathway VI) also appears as a central pathway releasing Glu and reducing equivalents; therefore, it is advantageous in highly energy-demanding developmental processes such as leaf senescence (Faes et al, 2015;Zhang and Becker, 2015). Here, we observed that the increase of transcript abundance of the two Arabidopsis Columbia-0 Pro dehydrogenases during senescence is similar.…”

Nitrogen use efficiency in rapeseed. A review

“…Another family was not affected by the N nutrition level but showed higher expression in stems than in leaves. Faes et al (2015) also demonstrated the differential expression of two subgroups of genes in the proline dehydrogenase gene family in rapeseed. These genes, ProDH1 and ProDH2, control proline catabolism, which is suspected to play a role in the remobilization of N from old to young leaves.…”

Connecting proline metabolism and signaling pathways in plant senescence

“…One observation is that during natural leaf aging proline catabolism appears to be upregulated via increased expression of PRODH2 and P5CDH . In Arabidopsis thaliana and Brassica napus (rapeseed), PRODH2 expression was strongly induced in the course of natural leaf aging ( Funck et al, 2010 ; Faes et al, 2015 ), whereas PRODH1 expression was moderately upregulated ( Funck et al, 2010 ). P5CDH expression was also reported to increase in older leaves of Arabidopsis ( Deuschle et al, 2004 ).…”