Characterization of transgenic Poncirus trifoliata overexpressing the ferric chelate reductase gene CjFRO2 from Citrus junos

Iron deficiency chlorosis occurs frequently in calcareous soils. The transformation of plants with ferric chelate
reductase genes (FROs) provides a potential strategy to alleviate plant chlorosis under iron deficiency. A CjFRO2 gene
isolated from Citrus junos Sieb. ex Tanaka was introduced into Poncirus trifoliata (L.) Raf via Agrobacterium-mediated
transformation. The transgene integration and expression were confirmed by PCR, Southern blot, and real-time PCR
analyses. Hydroponic- and soil-grown transgenic plants were tested for their tolerance to iron deficiency. Compared
with nontransgenic (NT) P. trifoliata plants, a rhizosphere acidification capacity in the transgenic lines increased, and a
ferric chelate reductase activity in roots was up to 3.39- and 2.93-fold higher in a hydroponic solution and soil,
respectively. A transgenic line TO-8, which reacted similarly in hydroponics and soil, appeared tolerant to the iron
deficiency. Its leaf chlorophyll and ferrous ion content was significantly higher than in NT. These results indicate that
tolerance to the iron deficiency in P. trifoliata could be improved through the genetic engineering.