Cultivated tomato has defects in both S-RNase and HT genes required for stylar function of self-incompatibility.
Cultivated tomato (Lycopersicon esculentum), a self-compatible species, evolved from self-incompatible (SI) species in the genus Lycopersicon following a breakdown of the self-incompatibility system. In order to elucidate the molecular basis of this breakdown in L. esculentum, we first analysed the stylar proteins with an in-gel assay for ribonuclease activity and 2D-PAGE. No S-RNase protein or its activity was detected in the style of L. esculentum. We then introduced the S6-RNase gene from an SI relative, L. peruvianum, into L. esculentum. However, the styles of transgenic plants expressing S6-RNase at levels comparable to those found in the L. peruvianum style were unable to reject self-pollen and L. peruvianum pollen in an allele-specific manner. This indicated that defect in the S-RNase expression was not the sole reason for the loss of self-incompatibility in tomato. The asparagine-rich HT protein, originally identified from the style of Nicotiana alata, is the other stylar factor involved in self-incompatibility reaction. We cloned and sequenced two distinct genes encoding HT-A and HT-B proteins from L. peruvianum (LpHT-A and LpHT-B) and L. esculentum (LeHT-A and LeHT-B). A frame shift mutation in the coding sequence of LeHT-A and a stop codon in the ORF of LeHT-B were found, and no LeHT-B transcript was detected in the style of L. esculentum. The results suggest that the breakdown of self-incompatibility in cultivated tomato is associated with loss-of-function mutations in both S-RNase and HT genes.
Kondo
Katsuhiko
K
Faculty of Bioresources, Mie University, Tsu 514-8507, Japan.
Yamamoto
Mayu
M
Matton
Daniel P
DP
Sato
Takanori
T
Hirai
Masashi
M
Norioka
Shigemi
S
Hattori
Tsukaho
T
Kowyama
Yasuo
Y
D000595:Amino Acid Sequence; D001483:Base Sequence; D018556:Crops, Agricultural / Q000235:genetics / Q000502:physiology; D005298:Fertility / Q000235:genetics; D018551:Solanum lycopersicum / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics* / Q000254:growth & development; D012260:Ribonucleases / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
C400763:HT protein, Nicotiana alata; D010940:Plant Proteins; D012260:Ribonucleases