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The kinetochore establishes the linkage between chromosomes and the spindle microtubule plus ends during mitosis. In vertebrates, the spindle-kinetochore-associated (Ska1,2,3) complex stabilizes kinetochore attachment with the microtubule plus ends, but how Ska is recruited to and stabilized at the kinetochore-microtubule interface is not understood. Here, our results show that interaction of Ska1 with the general microtubule plus end-associated protein EB1 through a conserved motif regulates Ska recruitment to kinetochores in human cells. Ska1 forms a stable complex with EB1 via interaction with the motif in its N-terminal disordered loop region. Disruption of this interaction either by deleting or mutating the motif disrupts Ska complex recruitment to kinetochores and induce chromosome alignment defects, but it does not affect Ska complex assembly. Atomic-force microscopy imaging revealed that Ska1 is anchored to the C-terminal region of the EB1 dimer through its loop and thereby promotes formation of extended structures. Furthermore, our NMR data showed that the Ska1 motif binds to the residues in EB1 that are the binding sites of other plus end targeting proteins that are recruited to microtubules by EB1 through a similar conserved motif. Collectively, our results demonstrate that EB1-mediated Ska1 recruitment onto the microtubule serves as a general mechanism for formation of vertebrate kinetochore-microtubule attachments and metaphase chromosome alignment.

The Tank Cascade System is one of the unique and socially accepted land-use practices in the dry zone of Sri Lanka which has evolved since 600 B.C. The small tank builders of the historical period had a profound and unified understanding of the natural resources, regional landscape, landforms, and hydrology. Tanks and irrigation canal systems, environmental zoning, forest reservations, agro-well-based land utilization, land-sharing system (Bethma), traditional soil conservation measures have been still maintaining well in some rural areas in the dry zone. Newly developed agro-well-based agro-forestry systems and some participatory techniques are also counted as few of sustainable land-use practices. This study has provided many valuable lessons of land use planning and management from the ancient hydraulic civilization and proving that the ancient system is still appropriate for the dry zone agricultural community rather than inadequately coordinated modern efforts of land use practices.

Carbonate rocks are highly soluble. Sinkholes are formed by both the failure of solution cavities and the rapid removal of fines from solution cavities in carbonate and metacarbonate rocks. Sri Lankan landmass is composed of Proterozoic high-grade metamorphic rocks such as gneiss and metacarbonates like marble. Large caves in Sri Lanka form in both marble and gneiss. A few land subsidence events have occurred recently in Ella-Wellawaya area, which is a hilly terrain. In addition, some cases of groundwater table lowering, which has caused drying of dug wells have also been recorded within the area, apparently related to a major development project presently under way in the area. The main objective of this paper is to draw the immediate attention of local researchers and authorities whom are working on mitigation and management of disasters, groundwater and climate change, showing the importance of carrying out detail studies on potential landslides and land subsidence of Ella-Wellawaya area for avoiding and minimising loss of humans and properties. Preliminary surveys on some land subsidence cases and speleological studies including geology, hydrogeology and morphological mapping of the underground caves in the area have been actively carried out. According to the results, it is shown that the subsidence is likely to be correlated with the collapsing of cavities and weathered zones in metacarbonates, and disturbances to the groundwater table. Field explorations done during the last two years have discovered several large underground caves in the area some more than 100 m across. Most of the cave roofs have been thinned by the breakdown of bedrock along weak zones such as joints. Since the process of collapse, trigged by weathering is continuing and patches and lenses of carbonate rocks observed in the caves are still being dissolved, the expansion of the cave spaces is unending. Some of the chambers of these caves are aligned parallel to the steep slopes in the Ella-Wellawaya area and some acted as underground water conduits and storages during the rainy seasons. The Ella-Wellawaya area has been undergone a change in vegetation cover since the colonial period and hence the area is more prone to soil erosion which exposes the near surface natural cavities to the underground caves. Present human exposures and interactions within the susceptible slopes have brought lives and properties under threat. Hence future land subsidence and landslide occurrences are highly predictable with the recent conditions in the area and hence threat to human life and properties is high. The tourism industry, unique to the area could particularly be affected. Hence such hazardous should properly be identified and demarcated and the erosion triggered by present vegetation changes must properly be addressed. Keywords: Metacarbonate rocks, Subsidence, Ella-Wellawaya, Cave network, Erosion