Articles
DEVELOPING TRANSGENIC PAPAYA WITH IMPROVED FUNGAL DISEASE RESISTANCE
Article number
864_3
Pages
39 – 44
Language
English
Abstract
Papaya (Carica papaya L.), one of the more important fruit crops of the tropics, has limited resistance to a range of fungal pathogens that may kill the plant or, at a minimum, reduce productivity and fruit quality.
Phytoalexins have been shown to be important natural components in the defense of plants against pathogen infection.
Several fruit crops, including grapes and peanuts, synthesize the stilbene-type phytoalexin, resveratrol, (trans-3,4, 5-trihydroxy-stilbene), when attacked by fungal pathogens such as, Botrytis cinerea or Plasmopara viticola. The level of resistance to P. viticola was positively correlated with the capacity of Vitis spp. to synthesize stilbene.
We conducted in-vitro pathogen inhibition assays to show that resveratrol also inhibited fungal pathogens of a tropical plant, papaya.
Resveratrol at 1.0 mM in V8 agar culture medium inhibited mycelial growth of Phytophthora palmivora by up to 50%, as compared to the control.
The compound was active against P. palmivora at concentrations as low as 100 µM. Resveratrol was not as effective against the anthracnose pathogen, Colletotrichum gloeosporiodes. Further, we transformed papaya embryogenic cultures with the stilbene synthase gene cloned from grapevine and driven by its own inducible promoter along with the hygromycin resistance or kanamycin resistance gene under the control of a CaMV35S promoter.
The presence of the transgenes was confirmed by PCR and Southern blot analysis.
Transgenic papaya plants were challenged with P. palmivora under greenhouse conditions.
Data from greenhouse studies showed that the disease levels in transgenics plant were reduced to 35% of the disease levels in non-transformed control plants.
Our findings indicated that metabolic engineering Carica papaya with heterologous phytoalexins, either under its own inducible promoter or a constitutive promoter, can improve plant defenses against fungal pathogens.
Phytoalexins have been shown to be important natural components in the defense of plants against pathogen infection.
Several fruit crops, including grapes and peanuts, synthesize the stilbene-type phytoalexin, resveratrol, (trans-3,4, 5-trihydroxy-stilbene), when attacked by fungal pathogens such as, Botrytis cinerea or Plasmopara viticola. The level of resistance to P. viticola was positively correlated with the capacity of Vitis spp. to synthesize stilbene.
We conducted in-vitro pathogen inhibition assays to show that resveratrol also inhibited fungal pathogens of a tropical plant, papaya.
Resveratrol at 1.0 mM in V8 agar culture medium inhibited mycelial growth of Phytophthora palmivora by up to 50%, as compared to the control.
The compound was active against P. palmivora at concentrations as low as 100 µM. Resveratrol was not as effective against the anthracnose pathogen, Colletotrichum gloeosporiodes. Further, we transformed papaya embryogenic cultures with the stilbene synthase gene cloned from grapevine and driven by its own inducible promoter along with the hygromycin resistance or kanamycin resistance gene under the control of a CaMV35S promoter.
The presence of the transgenes was confirmed by PCR and Southern blot analysis.
Transgenic papaya plants were challenged with P. palmivora under greenhouse conditions.
Data from greenhouse studies showed that the disease levels in transgenics plant were reduced to 35% of the disease levels in non-transformed control plants.
Our findings indicated that metabolic engineering Carica papaya with heterologous phytoalexins, either under its own inducible promoter or a constitutive promoter, can improve plant defenses against fungal pathogens.
Authors
Y.J. Zhu, R. Agbayani, C.S. Tang, P.H. Moore
Keywords
Carica papaya, Genetic transformation, root rot, Resveratrol (trans-3,4′,5-trihydroxy-stilbene), phytoalexins
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