Agriculture Reference
In-Depth Information
both genes are repressed by cold (CSIRO 2009). CSIRO is
locating and characterizing useful rice genes and addressing
rice tolerance to cold.
Pollen mother cells (PMC) under cold stress appeared
normal before meiosis, but during meiosis, normal callose
deposition was disrupted.
Consequently, the PMCs began to degenerate at the early
meiosis stage, eventually resulting in complete pollen collapse.
In addition, the degeneration of the tapetum and middle layer
was inhibited. These results demonstrate that rice Ugp1 is
required for callose deposition during PMC meiosis and bridges
the apoplastic unloading pathway and pollen development
(Fig. 25). UDP-glucose pyrophosphorylase (UDPase) catalyzes
the reversible production of glucose-1-phosphate and UTP to
UDP-glucose and pyrophosphate. The rice genome contains
two homologous UGPase genes, Ugp1 and Ugp2 (Chen et al.
2007).
Degeneration of tapetum
Cold stress
Pollen mother cells
(PMC)
Disruption of
callose
Degeneration of middle layer
Before meiosis
Complete pollen collapse
Fig. 25
Effects of cold stress before meiosis on pollen mother cells.
Low temperature may also result in non-receptive stigma,
fertilization failure or post fertilization development. These
important aspects of fl owering behavior in rice were studied by
Nizigiyimana (1990) who also reported that low temperature
