Identification of transcription factors potentially involved in the juvenile to adult phase transition in Citrus.
OBJECTIVE
The juvenile to adult transition (JAT) in higher plants is required for them to reach reproductive competence. However, it is a poorly understood process in woody plants, where only a few genes have been definitely identified as being involved in this transition. This work aims at increasing our understanding of the mechanisms regulating the JAT in citrus.


METHODS
Juvenile and adult plants from Pineapple sweet orange (Citrus sinensis) and Rough lemon (C. jambhiri) were used to screen for differentially expressed transcription factors (TFs) using a 1·15K microarray developed on the basis of the CitrusTF database. Murcott tangor (C. reticulata × C. sinensis) and Duncan grapefruit (C. paradisi) were incorporated into the quantitative real-time reverse transcription-PCR validation in order to select those genes whose phase-specific regulation was common to the four species.


RESULTS
A browsable web database has been created with information about the structural and functional annotation related to 1152 unigenes of putative citrus TFs (CTFs). This database constitutes a valuable resource for research on transcriptional regulation and comparative genomics. Moreover, a microarray has been developed and used that contains these putative CTFs, in order to identify eight genes that showed differential expression in juvenile and adult meristems of four different species of citrus. Those genes have been characterized, and their expression pattern in vegetative and reproductive tissues has been analysed. Four of them are MADS-box genes, a family of TFs involved in developmental processes, whereas another one resembles MADS-box genes but lacks the MADS box itself. The other three showed high partial sequence similarity restricted to specific Arabidopsis protein domains but negligible outside those domains.


CONCLUSIONS
The work presented here indicates that the JAT in citrus could be controlled by mechanisms that are in part common to those of Arabidopsis, but also somehow different, since specific factors without Arabidopsis orthologues have also been characterized. The potential involvement of the genes in the JAT is discussed.
Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Carretera Moncada-Náquera, Km. 4·5, 46113 Moncada (Valencia), Spain.
Mari-Cruz
MC
Castillo
Javier
J
Forment
José
J
Gadea
Jose Luis
JL
Carrasco
José
J
Juarez
Luís
L
Navarro
Gema
G
Ancillo
D002957:Citrus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D019295:Computational Biology; D030541:Databases, Genetic; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018519:Meristem / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors
C. jambhiri; C. paradisi; C. reticulata; Citrus sinensis; JAT; database; differential gene expression; juvenile to adult transition; juvenility; transcription factor