LIBRO-CONGRESO-CITRUS

S03
S03O07
Analysis of the clementine floral transcriptome uncovers candidate genes involved in selfincompatibility
Caruso M. 1 , Lo Cicero L. 1 , Distefano G. 1 , Merelo P. 2 , La Malfa S. 1 , Tadeo F.R: 2 , Talón M. 2 , Lo Piero A.R. 1 , and Gentile A. 1
1 University of Catania (DISPA), Department of Agriculture and Food Science, Italy; and 2 Instituto Valenciano de Investigaciones
Agrarias (IVIA), Centro de Genómica, Spain. gentilea@unict.it
Self-incompatibility (SI), typical of many mandarin and pummelo varieties, is a valuable trait to obtain seedless
fruits. Despite the importance of SI, the genetic basis of this trait in citrus is poorly understood. Two clementine
genotypes showing divergent behaviour related to self-pollen rejection (‘Comune’, self-incompatible’; and
‘Monreal’, self-compatible) were chosen as model to study the molecular events occurring during pollen-pistil
interaction and the self-incompatible response. The comparative analysis of the floral transcriptome of the two
clementine genotypes led to identifying a set of candidate genes related to SI. The identified genes show no
homology to SI genes of other plant species and lack annotation. Functional analyses are therefore needed to
unravel their function and to confirm their role in the citrus progamic phase. Our attention focused on 4 genes
over- represented in the’ Comune’ transcriptome whose expression drastically increased in concomitance with
the halting of pollen tube elongation, namely a putative F-box protein gene and three aspartic-acid rich (Asprich)
protein encoding genes. A first step of the functional characterization consisted in their over-expression
in tobacco plants. Moreover, the Asp-rich proteins were expressed in a cell-free system and purified for a
biochemical characterization. The preliminary results of the functional analyses are discussed.
S03O08
Citrus gene function analysis using a viral vector based on the Citrus leaf blotch virus genome
Agüero J., Velázquez K., Vives M.C., Pina J.A., Navarro L., Moreno P., and Guerri J.
Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Mocada, Valencia, Spain.
jaguero@ivia.es
Genetic improvement of citrus by conventional breeding is hindered by their complex reproductive biology, high
heterozygosis and long juvenile period (up to 6-8 years). Moreover, the genes responsible for each biological
process are presently unknown. Since viral vectors allow rapid testing of gene function, they may be a better
tool than transgenic expression for improvement of citrus, whose adult plants are difficult to transform. We
have developed vectors based on the Citrus leaf blotch virus (CLBV) genome by i) introducing in a full-genome
infectious cDNA clone a unique restriction site in the 3’ untranslated region (clbv3´ vectors) or at the intergenic
region between the movement protein and the coat protein (CP) genes (clbvIN vectors), and ii) duplicating
in these positions a minimum promoter derived from the natural promoter sequence of the CP subgenomic
RNA. When fragments of the phytoene desaturase, magnesium chelatase or actin genes were cloned in those
vectors and then inoculated onto different citrus species all plants showed the silencing phenotype and reduced
accumulation of the cognate mRNAs. This phenotype was observed in successive flushes for at least 2 years
and the inserts remained stable as tested by RT-PCR with primers flanking the insertion site. Expression of the
FLOWERING LOCUS T in young seedlings using those vectors incited flowering in just 4 months. This dramatic
reduction of the juvenile period may be a useful tool for citrus genetic improvement.
S03P01
Expression analysis of genes differentially expressed in stem tissue of two lemon cultivars.
Koutsioumari E.M., and Voloudakis A.E.
Agricultural University of Athens (AUA), Laboratory of Plant Breeding and Biometry, Department of Crop Science, Greece.
eva.kouts@yahoo.gr
Lemon (Citrus limon) cultivation in Greece and other Mediterranean countries suffers from two major problems:
the destructive disease Mal Secco caused by the fungus Phoma tracheiphila and chilling injury caused by low
temperatures. The knowledge of genes involved in resistance to the above mentioned stresses would be useful
in breeding tolerant lemon cultivars. In order to determine the molecular basis of resistance to these stresses,
64 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012