LIBRO-CONGRESO-CITRUS

S07O06
Exploring microRNA target modulation in citrus somatic embryogenesis by high-throughput
small RNA and degradome sequencing
Wu X.M., Liu M.Y., Xu Q., Deng X.X., and Guo W.W.
Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University (HZAU), China.
ema@webmail.hzau.edu.cn
Somatic embryogenesis (SE) from callus is an important approach of in vitro regeneration, as well as a model
for studying mechanisms of nucellar polyembryony in citrus. In our study, small RNA (sRNA) and degradome
(the collection of molecules that result from the incomplete degradation of mature, functional RNAs)
sequencing were implemented on embryogenic callus (EC) and non-embryogenic callus (NEC) of ‘Valencia’
sweet orange, as well as on EC cultured on glycerol medium for 1-4 weeks (E1-4) on which somatic embryos
were induced. A total of 64 previously known and 191 novel microRNAs (miRNAs) were identified. Quite
a few miRNAs were found to be highly expressed in NEC, while only 25 miRNAs were more abundant in
embryogenic tissues than in NEC. miRNA expression was detected in preserved callus of seven citrus varieties
with different SE capability. Five miRNAs, miR156, 164, 390, 171 and 059, were found to be expressed higher
in callus with SE capability compared to callus that had lost SE capability. In addition, 1,150 transcripts were
identified to be cleaved by 129 miRNAs in the three tissues (EC, NEC, E1-4). A total of 347 phased siRNA
(phasiRNA) were identified and most highly expressed in NEC and only two expressed higher in EC or E1-4
tissue than in NEC. For the over-accumulation of one of the most conserved miRNAs, miR156 in EC and
SE processes of ‘Valencia’, the Csi-MIR156 gene was overexpressed by a 35S promoter in ‘Guoqing No. 1’
satsuma mandarin (Citrus unshiu), which had lost SE capability over years. Although the SE capability was not
recovered, the overexpression lines tended to accumulate significantly more amyloids, which resembled EC
cells of ‘Valencia’ with strong SE capability.
S07P01
Periods of normal and induced vegetative and reproductive shoots of ‘Persian’ lime (Citrus latifolia)
Medina-Urrutia V.M. 1 , Durán-Martínez C.M. 2 , Virgen-Calleros G. 2 , Robles-González M.M. 2 , and Rendon-Salcido L.A. 2
1Universidad de Guadalajara (CUCBA-UDG), Centro Universitario de Ciencias Biológicas y Agropecuarias, México; and 2Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias (INIFAP-Colima), CIRPAC, México. vmmedinau@gmail.com
‘Persian’ lime fruit is mainly produced under tropical conditions in the State of Veracruz in México. As the
demand in international markets has increased, new lime orchards also were established in subtropical
regions. Information about the phenological performance of ‘Persian’ lime trees under this climate is
scarce. The objective of this work was to determine the time of vegetative (VEG) and reproductive (REP)
sprouting of ‘Persian’ lime trees under subtropical conditions of Jalisco State in México. Two orchards
of lime trees budded on ‘Volkamer’ lemon (C. volkameriana) rootstock and planted on clay soils were
selected. The first site was located at San Martin Hidalgo (SMH) at 1518 m of altitude, mean temperature
of 16.7 to 24.4 °C and average annual rainfall of 908 mm. The second orchard was planted in Atotonilco
(ATO) at 1606 m of altitude, mean temperature of 15.7 to 22.6 °C and with 856 mm of rainfall. Tree age was
six- and four-years-old at SMH and ATO respectively. VEG and REP shoots were recorded biweekly during
two years. Results showed that periods of VEG and REP shoots were very similar in both regions. Two peaks
of VEG shoots were detected, one initiated in middle winter (February) and the second in middle summer
(end of June-beginning of July). The production of VEG shoots during the summer season was 3 fold greater
than the winter sprouting. VEG sprouting extended 15-40 days more during winter than in the summer
season. Both mixed and REP shoots were also produced in a higher proportion during summer than in the
winter season. VEG and REP shoots emerged in summer time were induced by a treatment of water stress
applied before the initial rainy season. Normal REP and VEG shoots emerged during winter were associated
with lower night temperatures (6 to 13 °C) and higher day temperatures (24 to 29 °C) recorded during this
period. Fruits initiated in the summer bloom required 130-145 day to harvest. Flowering during winter
time preceded harvest by more than 150 days.
XII INTERNATIONAL CITRUS CONGRESS 2012 - 109
S07