Han Zhang, Abstract
By RNA profiling of ten stages of maize anthers plus mature pollen, we found two novel classes of phased small-interfering RNAs (phasiRNAs): 21-nt pre-meiotic phasiRNAs after germinal and somatic cell specification; 24-nt meiotic phasiRNAs coordinately accumulate during meiosis and persist into pollen. Sequencing of five male-sterile, anther developmental mutants -- ocl4, mac1, ms23, msca1, and ameiotic1 -- demonstrated the involvement of specific somatic layers. Pre-meiotic phasiRNAs require a functional epidermis while meiotic phasiRNAs require a normal tapetum. CRISPR is used to target genes and miRNA triggers required for phasiRNA biogenesis and function.
Masayoshi Nakamura, Abstract
Plants perceive and respond to environmental cues. As sessile organisms one important such response is directional cell growth. Genetic and pharmacological studies have shown that cortical microtubule networks just beneath the plasma membrane play a critical role in growth direction of plant cells through the cell wall. Cortical microtubules can undergo dramatic reorientation in response to environmental cues. For instance, blue light causes a significant rearrangement of cortical microtubules in dark-grown hypocotyl cells, in which transversely oriented microtubules are shifted to a longitudinal direction. This reorientation is driven largely by Katanin-mediated severing and amplification of new growing ends at microtubule crossovers. Katanin is recruited to microtubule crossovers, however, little is known about how the cell regulates Katanin dynamics and activity. We are currently in the of characterizing the dynamics and regulation of microtubule severing.