Ephrin-B2, a member of the Eph/ephrin family of cell signaling molecules, has been implicated in the guidance of cranial and trunk neural crest cells (NCC) and development of the branchial arches(BA), but detailed examination in mice has been hindered by embryonic lethality of Efnb2 null loss of function due to a requirement in angiogenic remodeling. To elucidate the developmental roles for Efnb2, we generated a conditional rescue knock-in allele that allows rescue of ephrin-B2 specifically in the vascular endothelium (VE), but is otherwise ephrin-B2 deficient. Restoration of ephrin-B2 expression specifically to the VE completely circumvents angiogenic phenotypes, indicating that the requirement of ephrin-B2 in angiogenesis is limited to the VE. Surprisingly, we find that expression of ephrin-B2 specifically in the VE is also sufficient for normal NCC migration and that conversely, embryos in which ephrin-B2 is absent specifically from the VE exhibit NCC migration and survival defects. Disruption of vascular development independent of loss of ephrin-B2 function also leads to defects in NCC and BA development. Together, these data indicate that direct ephrin-B2 signaling to NCCs is not required for NCC guidance, which instead depends on proper organization of the embryonic vasculature.

SlARF2a is expressed in most plant organs, including roots, leaves, flowers and fruits. A detailed expression study revealed that SlARF2a is mainly expressed in the leaf nodes and cross-sections of the nodes indicated that SlARF2a expression is restricted to vascular organs. Decapitation or the application of 6-benzylaminopurine (BAP) can initially promote axillary shoots, during which SlARF2a expression is significantly reduced. Down-regulation of SlARF2a expression results in an increased frequency of dicotyledons and significantly increased lateral organ development. Stem anatomy studies have revealed significantly altered cambia and phloem in tomato plants expressing down-regulated levels of ARF2a, which is associated with obvious alterations in auxin distribution. Further analysis has revealed that altered auxin transport may occur via altered pin expression. To identify the interactions of AUX/IAA and TPL with ARF2a, four axillary shoot development repressors that are down-regulated during axillary shoot development, IAA3, IAA9, SlTPL1 and SlTPL6, were tested for their direct interactions with ARF2a. Although none of these repressors are directly involved in ARF2a activity, similar expression patterns of IAA3, IAA9 and ARF2a implied they might work tightly in axillary shoot formation and other developmental processes.

Western blotting is a powerful tool for assessing the presence and modification of a protein. No suitable reference proteins for barley (Hordeum vulgare L.) western blotting has identified. In this study, we compared the quality of the total protein extracted from barley leaves, roots, and seeds using the Tris, QB, direct, phenol, TCA and modified TCA methods. The results confirmed the Tris, direct and modified TCA methods were optimal for seeds, young tissues and mature tissues protein extracting, respectively. The stability and sensitivity among the three reference proteins, i.e., plant actin, heat shock protein 90, and histone H3, during barley western blotting among were compared in different tissues/organs at various stages of development and/or stress. The results showed that plant actin was the most sensitive and the most constantly expressed among all the reference proteins tested in all barley organs. A linear relationship (R=0.9710) of the plant actin signal intensity with the sample amount was detected when the total protein ranged within 10-160 µg. The optimized barley western blotting procedure was used to investigate the response of H3K27me1 and H3K27me3 to waterlogging in barley. Under waterlogging, the expression of H3K27me1 was repressed in the stems but promoted in the roots, while the expression of H3K27me3 was repressed in both the leaf and stem. This is the first report about H3K27 methylation modifications displayed the organspecific response patterns to waterlogging in barley.

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