Diversification in flowering time due to tandem FT-like gene duplication, generating novel Mendelian factors in wild and cultivated rice

The complex structure of a single Mendelian factor widespread in the Asian cultivated rice ( Oryza sativa ) and its wild progenitor ( Oryza rufipogon ) that caused diverse phenotypes in the timing of flowering under natural field conditions was investigated in near isogenic lines. These near isogenic lines showed differences in flowering time despite all eight accessions collected from tropical regions possessing a recessive gene allelic to the se-pat gene. Fine mapping in two of these near-isogenic lines revealed that cultivated (Patpaku) and wild (W593) accessions had three and two linked quantitative trait loci (QTL) in the candidate regions, respectively, showing that Patpaku and W593 possessed linked QTLs with different effects in addition to the commonly-observed recessive gene ( se-pat ). Molecular dissection suggested that the tandemly duplicated FT-like genes ( Hd3a and RFT1 ) could be the candidate genes for these QTLs. Interestingly, the linked QTLs differed in their epistases, degree of dominance, and genotype × environment interactions. The nucleotide sequences showed that RFT1 has diverged more rapidly than Hd3a during rice evolution, suggesting phenotypic diversification of the two genes. Phylogenetic analysis implied that the se-pat ⁺ alleles might have emerged in different lineages within O. sativa . The present results strongly suggest that nucleotide divergence and shuffling of the linked QTLs by recombination might have created novel Mendelian factors that probably contribute to responding to local environments.     

The translocation of photosynthetic products from mesophyll into midrib in tobacco plant III. The transformation of translocated 14C-sugars in the veins

¹⁴C-U-sugars were introduced into tobacco plants through themesophyll, the veins of the first order of branching, and themidrib, and ¹⁴C-compounds in the veins and the midrib whichtranslocated towards the base of the midrib were traced duringthe period of 120 min after the ¹⁴C-sugar introductions. 1) When ¹⁴C-U-sucrose was introduced into the leaf, no matterwhat the means of feeding was, most of the ¹⁴C which translocatedbasipetally in the veins and the midrib was found in the formof sucrose. 2) When ¹⁴C-U-glucose or ¹⁴C-U-fructose was administered tothe leaf dirough the cut vein of the first order of branching,most of the ¹⁴C which translocated basipetally in the veinsand the midrib was found in the form of sucrose. 3) ¹⁴C-U-glucose or ¹⁴C-U-fructose injected into the vascularbundles of the midrib was translocated basipetally, as such,10 and 30 min after injection; and at 30 min, the amount ofthe ¹⁴C-sucrose in the midrib attained 9–22% of the 80%ethanol-soluble ¹⁴C in the midrib. 4) When ¹⁴C-U-glucose or ¹⁴C-U-fructose was supplied to themesophyll, the radioactivities of these hexoses were predominantin the first and second veins soon after application, then decreasingwith a concomitant increase in the radioactivity of the ¹⁴C-sucrose. From these results, it was inferred that in the veins of thefirst and second order of branching, glucose and fructose whichmoved from the mesophyll did not translocate as such, but wereutilized for the synthesis of sucrose available for translocationvia the midrib to the stem. ¹A part of this paper was presented at the Crop Science Societyof Japan, in April, 1969 (Received December 8, 1969; )     

Partial Synchronization of Carrot Cell Culture by Auxin Deprivation

A strain of carrot cells (Daucus carota cv. Kintoki) grew exponentially in the presence of 2,4-dichlorophenoxyacetic acid (2,4-D, 1 mg/1) with a doubling time of about 2 days. When those cells were transferred to a medium lacking 2,4-D, they continued to grow at almost the same rate for about a week. When the cells were again transferred to the auxin-free medium, the rate of cell division gradually decreased. After the cell division had ceased, cells were returned to the ordinary 2,4-D medium. A burst of cell divisions occurred after about 2 days. Timing of DNA synthesis and of mitosis suggested that the cells had been arrested at G₁ phase. In a medium containing indoleacetic acid instead of 2,4-D, the auxin was rapidly degraded and the culture was similarly synchronized as in the auxin-omitted medium.     

THE SURFACE EVENTS AT FERTILIZATION OF THE SEA URCHIN EGG I. EVENTS ON THE SURFACE OF THE VITELLINE COAT1

Sperm-egg interaction during normal fertilization in the sea urchins, Strongylocentrotus intermedius and Hemicentrotus pulcherrimus, was studied by scanning and transmission electron microscopy. Several seconds after insemination, acrosome-reacted spermatozoa were found attached to the surface of the vitelline coat on each egg. Soon, several bulges of the vitelline coat appeared surrounding the fertilizing spermatozoon. These bulges then spread over the surface increasing in number, while they became fewer and disappeared around the sperm head. Thin sections of the bulging areas revealed discharging cortical granules. As the bulging vitelline coat was elevated, the sperm head was incorporated into the perivitelline space, passing through a small hole in the coat that resulted from penetration of the sperm acrosomal process immediately before fusion of the gametes. When the spermatozoon disappeared beneath the fertilization membrane, a hole was left in the membrane and the cortical reaction had finished on the other hemispheric surface. Mechanical removal of the membrane at that time exposed a spermatozoon protruding perpendicularly from the egg plasma membrane surface. The anterior tip of the sperm head was smoothly connected with the egg surface, and neither microvillous projections nor cytoplasmic covering of the egg cytoplasm could be found around the spermatozoon.     

High temperature causes arrest of cell cycle in G2 phase in BmN cells derived from the silkworm, Bombyx mori

Abstract.  The influence of temperature on the insect cell line, BmN, derived from the silkworm, Bombyx mori is investigated. These cells proliferate at an accelerated pace as the temperature increases from 22 to 30 °C, but the growth rate slows at 34 °C, and proliferation stops at 38 °C. At high temperatures, abnormal cellular morphology is observed. Cells treated at 38 °C have cytoplasmic bilateral protrusions and they gradually aggregate and float in the medium. BmN cells without proliferation at 38 °C are viable but have reduced DNA synthesis. At high temperatures, the cell cycle of BmN cells halts at the G₂ phase. After heat treatment of the larvae, an accumulation of larval haemocytes with high DNA content is found, which suggests that the cell cycle arrest at G₂ also occurs in the silkworm at high temperatures.     

Taxonomic identity of a galling adelgid (Hemiptera: Adelgidae) from three spruce species in Central Japan

Gall‐forming insects are commonly highly host‐specific, and galling species once thought to be oligo‐ or polyphagous are often found to represent a complex of host‐specific races or cryptic species. A recent DNA barcoding study documented that an unidentified species of the genus Adelges is a gall‐former associated with four spruce species (Picea bicolor, P. koyamai, P. maximowiczii, P. polita) as the primary hosts, with little genetic differentiation among insects on different host species. In this study, we investigated the morphology of this galling adelgid to determine its taxonomic identity. Morphological inspection of insects collected from three of the spruce species confirmed that this adelgid is a single galling species, and is identified as Adelges (Sacchiphantes) kitamiensis, which was previously known only from the secondary host. We described the gallicola adults of this species, as well as the first‐instar exules which are the offspring of gallicolae. Finally, we verified the taxonomic identity of this species and discuss its life cycle and host distribution.