Tig1 regulates proximo-distal identity during salamander limb regeneration

Salamander limb regeneration is an accurate process which gives rise exclusively to the missing structures, irrespective of the amputation level. This suggests that cells in the stump have an awareness of their spatial location, a property termed ‘positional identity’. Little is known about how positional identity is encoded, in salamanders or other biological systems. Through single-cell RNAseq analysis, we identified Tig1/RARRES1 as a potential determinant of proximal identity. Tig1 encodes a conserved cell surface molecule, is regulated by retinoic acid and exhibits a graded expression along the proximo-distal axis of the limb. Its overexpression leads to regeneration defects in the distal elements and elicits proximal displacement of blastema cells, while its neutralisation blocks proximo-distal cell surface interactions. Critically, Tig1 reprogrammes distal cells to a proximal identity, upregulating Prod1 and inhibiting HoxA13 and distal transcriptional networks. Thus, Tig1 is a central cell surface determinant of proximal identity in the salamander limb.

Auxin biosynthesis and cellular efflux act together to regulate leaf vein patterning

Our current understanding of vein development in leaves is based on canalization of the plant hormone auxin into self-reinforcing streams which determine the sites of vascular cell differentiation. By comparison, how auxin biosynthesis affects leaf vein patterning is less well understood. Here, after observing that inhibiting polar auxin transport rescues the sparse leaf vein phenotype in auxin biosynthesis mutants, we propose that the processes of auxin biosynthesis and cellular auxin efflux work in concert during vein development. By using computational modeling, we show that localized auxin maxima are able to interact with mechanical forces generated by the morphological constraints which are imposed during early primordium development. This interaction is able to explain four fundamental characteristics of midvein morphology in a growing leaf: (i) distal cell division; (ii) coordinated cell elongation; (iii) a midvein positioned in the center of the primordium; and (iv) a midvein which is distally branched. Domains of auxin biosynthetic enzyme expression are not positioned by auxin canalization, as they are observed before auxin efflux proteins polarize. This suggests that the site-specific accumulation of auxin, as regulated by the balanced action of cellular auxin efflux and local auxin biosynthesis, is crucial for leaf vein formation.

Fgf-signaling is compartmentalized within the mesenchyme and controls proliferation during salamander limb development

Although decades of studies have produced a generalized model for tetrapod limb development, urodeles deviate from anurans and amniotes in at least two key respects: their limbs exhibit preaxial skeletal differentiation and do not develop an apical ectodermal ridge (AER). Here, we investigated how Sonic hedgehog (Shh) and Fibroblast growth factor (Fgf) signaling regulate limb development in the axolotl. We found that Shh-expressing cells contributed to the most posterior digit, and that inhibiting Shh-signaling inhibited Fgf8 expression, anteroposterior patterning, and distal cell proliferation. In addition to lack of a morphological AER, we found that salamander limbs also lack a molecular AER. We found that amniote and anuran AER-specific Fgfs and their cognate receptors were expressed entirely in the mesenchyme. Broad inhibition of Fgf-signaling demonstrated that this pathway regulates cell proliferation across all three limb axes, in contrast to anurans and amniotes where Fgf-signaling regulates cell survival and proximodistal patterning.

Incidence of blossom-end rot in elongated tomato fruit

Blossom-end rot (BER) is a physiological disorder that can affect 100% of the fruit crop depending on the genotype. Tomato varieties with elongated fruit usually have a greater susceptibility to BER than other varieties. To evaluate and identify the possible physiological and morphological characteristics related to the onset of BER development, four varieties of long-shape tomato fruit with different susceptibility to BER: ‘San Marzano,’ ‘Banana Legs,’ ‘Roma,’ and ‘Mini-Roma’ were examined. Our results show that ‘San Marzano’ and ‘Banana Legs’ (elongated fruit) had a higher incidence of BER and lower Ca2+ concentration in the distal fruit tissue. ‘San Marzano’ (the most elongated fruit) presented higher electrolyte leakage in the distal fruit tissue. By comparison, ‘Roma’ and ‘Mini-Roma’ (less elongated fruit) were less susceptible to BER and had a higher ratio for proximal/distal fruit Ca2+ and a lower distal cell-wall bound content of Ca2+. Additionally, xylem functionality (vessels transporting water and solutes) in the distal fruit tissue was also higher in these more-tolerant varieties. These results support the theory that total fruit content of Ca2+ is not the only factor determining fruit susceptibility to BER, but rather a balance between physiological and morphological factors that influence Ca2+ transport and allocation in the fruit.

New Stenting Technique to Achieve Favorable Jailing Configuration on Side Branch Ostium: Bent Stent Technique

According to data from stent-enhanced three-dimensional optical coherence tomography, incomplete stent apposition after side branch dilation in coronary bifurcation stenting can be reduced by the free carina type (no links bridged from a carina) and by distal cell rewiring. This is the first report to describe a bent stent technique that was devised to achieve the free carina type (no links bridged from a carina), as a favorable jailing configuration.

Instant Stent-Accentuated Three-Dimensional Optical Coherence Tomography Guided Selection of Proper Distal Cell for Side Branch Dilatation in Bifurcation Stenting

In the bifurcation stenting, the distal rewiring for the side branch postdilatation confirmed by two-dimensional modalities may not lead to favorable results in some cases. If there are two distal cells divided by the link bridging from the carina, the rewiring through the larger distal cell may be recommended for the side branch postdilatation. Detailed confirmation of the rewired cell by the intraprocedural instant stent-accentuated three-dimensional optical coherence tomography is important.

Space botany in Lithuania. I. Root gravisensing system formation during satellite “Bion-10” flight

Švegždienė D., Raklevičienė D., Koryzienė D., 2013: Space botany in Lithuania. I. Root gravisensing system formation during satellite “Bion-10” flight [Kosminė botanika Lietuvoje. I. Gravitaciją juntančių šaknų ląstelių formavimasis palydovo „Bion-10“ skrydžio metu]. - Bot. Lith., 19(2): 129-138. The paper deals with the results of space experiment, which was carried out on an original automatically operating centrifuge „Neris-5“ on board of the satellite „Bion-10“ in 1993. The peculiarities of gravisensing system formation in roots of garden cress (Lepidium sativum L.) seedlings grown in microgravity under simulated and natural gravity of 1g in space and on the ground, respectively, are presented. Quantitative study on the growth of root columella cells (statocytes), the state of their intracellular components, and the location of amyloplasts was performed by light and electron microscopy. The growth of statocytes in microgravity and under 1g in space did not differ significantly though the location of amyloplasts experienced significant changes: it depended on the gravity and cell position in columella. Instead of the concentration of amyloplasts at the distal cell region of roots grown under 1g, most plastids in microgravity-grown roots were accumulated at the centre of statocytes. The obtained data on the formation and state of intercellular plastids confirm the supposition that the environment of microgravity alters the metabolism of plant cells; however, its alterations are not fateful for the formation of gravisensing cells and for the growth of the whole root.