Localization in roots and flowers of pea chloroplastic thioredoxin f and thioredoxin m proteins reveals new roles in nonphotosynthetic organs.
Plant thioredoxins (TRXs) are involved in redox regulation of a wide variety processes and usually exhibit organ specificity. We report strong evidence that chloroplastic TRXs are localized in heterotrophic tissues and suggest some ways in which they might participate in several metabolic and developmental processes. The promoter regions of the chloroplastic f and m1 TRX genes were isolated from a pea (Pisum sativum) plant genomic bank. Histochemical staining for beta-glucuronidase (GUS) in transgenic homozygous Arabidopsis (Arabidopsis thaliana) plants showed preferential expression of the 444-bp PsTRXf1 promoter in early seedlings, stems, leaves, and roots, as well as in flowers, stigma, pollen grains, and filaments. GUS activity under the control of the 1,874-bp PsTRXm1 promoter was restricted to the leaves, roots, seeds, and flowers. To gain insight into the translational regulation of these genes, a series of deletions of 5' elements in both TRX promoters were analyzed. The results revealed that a 126-bp construct of the PsTRXf2 promoter was unable to reproduce the expression pattern observed with the full promoter. The differences in expression and tissue specificity between PsTRXm1 and the deleted promoters PsTRXm2 and PsTRXm3 suggest the existence of upstream positive or negative regulatory regions that affect tissue specificity, sucrose metabolism, and light regulation. PsTRXm1 expression is finely regulated by light and possibly by other metabolic factors. In situ hybridization experiments confirmed new localizations of these chloroplastic TRX transcripts in vascular tissues and flowers, and therefore suggest possible new functions in heterotrophic tissues related to cell division, germination, and plant reproduction.
de Dios Barajas-López
Juan
J
Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain.
Serrato
Antonio Jesús
AJ
Olmedilla
Adela
A
Chueca
Ana
A
Sahrawy
Mariam
M
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D054479:Chloroplast Thioredoxins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant; D035264:Flowers / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D011994:Recombinant Proteins
D029681:Arabidopsis Proteins; D054479:Chloroplast Thioredoxins; D018744:DNA, Plant; D011994:Recombinant Proteins; C000590494:TRX m1 protein, Arabidopsis; C000590495:TRX m2 protein, Arabidopsis