Earliest floral evidence for the Ebenaceae in Australia
Flowers are seldom preserved in an identifiable condition. The limited knowledge of floral structure of ancient flowering plants makes comparisons with living plants difficult, as floral structure is the basis for classification of the angiosperms. When found, fossil flowers contribute considerably to our understanding of the evolution of flowering plants1–6. The flowers described here were recovered from Upper Eocene deposits near Anglesea, Australia. They are tetramerous, unisexual, male, with 16 stamens and tricolporate pollen. These flowers, and associated ebenaceous leaves, are the oldest known remains of the Ebenaceae from Australia.
A Y-chromosome–encoded small RNA acts as a sex determinant in persimmons
Y male plants affect female development Although most plants have both male and female organs within a single flower, some produce separate male and female plants. In some cases, such as persimmons, males are determined by a Y chromosome. Akagi et al. examined the gene transcript differences between male and female persimmons. A gene on the Y chromosome regulated a non–sex chromosome–linked small RNA that suppresses female organ development. This small RNA was localized to male flowers and could affect female development in other plant species. The evolutionary history of these genes suggests that they are tied to the origin of the separation of sexes in the persimmon family. Science, this issue p. 646 The Y chromosome in date plum encodes a small RNA involved in male sex determination. In plants, multiple lineages have evolved sex chromosomes independently, providing a powerful comparative framework, but few specific determinants controlling the expression of a specific sex have been identified. We investigated sex determinants in the Caucasian persimmon, Diospyros lotus, a dioecious plant with heterogametic males (XY). Male-specific short nucleotide sequences were used to define a male-determining region. A combination of transcriptomics and evolutionary approaches detected a Y-specific sex-determinant candidate, OGI, that displays male-specific conservation among Diospyros species. OGI encodes a small RNA targeting the autosomal MeGI gene, a homeodomain transcription factor regulating anther fertility in a dosage-dependent fashion. This identification of a feminizing gene suppressed by a Y-chromosome–encoded small RNA contributes to our understanding of the evolution of sex chromosome systems in higher plants.
Remotely-Piloted Helicopter Citrus Yield Map Estimation
A remotely-piloted Gas Xcell mini-helicopter with GPS, wireless Ethernet, and a machinevision system was flown over orange trees to take overhead images. The individual tree images were processed to estimate the number of orange pixels in the images. The fruit yield of individualtrees at harvest a month later had an r-squared value of 0.373 with the number of orange pixels onthe irrigated tree images. While it was demonstrated that a remotely-piloted mini-helicopter could beused to acquire useful overhead images of citrus trees, substantial further research is needed toimprove the accuracy of estimates of individual tree yields or health.