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The ParABS system is essential for prokaryotic chromosome segregation. After loading at parS on the genome, ParB (partition protein B) proteins rapidly redistribute to distances of ~15 kilobases from the loading site. It has remained puzzling how this large-distance spreading can occur along DNA loaded with hundreds of proteins. Using in vitro single-molecule fluorescence imaging, we show that ParB from Bacillus subtilis can load onto DNA distantly of parS, as loaded ParB molecules themselves are found to be able to recruit additional ParB proteins from bulk. Notably, this recruitment can occur in cis but also in trans, where, at low tensions within the DNA, newly recruited ParB can bypass roadblocks as it gets loaded to spatially proximal but genomically distant DNA regions. The data are supported by molecular dynamics simulations, which show that cooperative ParB-ParB recruitment can enhance spreading. ParS-independent recruitment explains how ParB can cover substantial genomic distance during chromosome segregation, which is vital for the bacterial cell cycle.

For rainfed low land paddy ecosystems which is supposed to withstand the sudden rise of water level for short period of time i.e. up to two weeks has been considered as the submergence tolerant. Proper screening and evaluation method are very important for cost effective and economic breeding procedures that will benefits the farmers. The agro morphological characters which are responsible for submergence tolerance; character association and path coefficient analysis will be very much useful to select them for further assessment. Hybrid rice will be another approach which could mitigate the flash flood constraints. Proper understanding of anatomical characters such as aerenchyma formation and changes of diameter of aerenchyma of root, shoot and leaf will be very much important for submergence tolerance if it is linked with genetic factors. Biochemical manipulation of different plant hormone such as gibberellic acid, abscisic acid and ethylene; enzyme like alcohol dehydrogenase synthesis; chlorophyll content and non structural carbohydrate content of shoot has significant role for enhancement of survival during underwater growth. Plant extracts or herbal crude product in the form of dry and wet treatments along with proper growth nutrients will be a holistic approach for sustainable and integrated agriculture and will be a tool for crop improvement in future breeding programme for submergence tolerance in rice.

Fifty diverse paddy genotypes were evaluated under low land submerged field condition at two different locations i.e. Hingalganje (North 24 Pgs, West Bengal) and Baruipur (South 24 Pgs, West Bengal) during the kharif seasons for three consecutive years of 2011, 2012 and 2013 for the study of association between yield and yield components under submerged condition where the water depth was more than 50 cm at least for two weeks at the vegetative stage of crop. On the basis of mean performances genotypes viz., Mahananda, Sabita, Nagalmuda, Lakshmikajal, Purnendu and Jaladhi II performed better for seed yield than the tolerant checks. High broad sense heritability along with high genetic gain over mean was also observed for plant height, grains/panicle, test weight, and seed yield. Fertile grains per panicle, panicle length and test weight (1000 seed weight) are consistently highly positively correlated with the seed yield. These yield attributes were the major contributing traits for seed yield in rice under submergence in the set of genotypes under study.

Structural maintenance of chromosomes (SMC) protein complexes play pivotal roles in genome organization and maintenance across all domains of life. In prokaryotes, SMC family Wadjet complexes structurally resemble the widespread MukBEF genome-organizing complexes but serve a defensive role by inhibiting plasmid transformation. We previously showed that Wadjet specifically cleaves circular DNA; however, the molecular mechanism underlying DNA substrate recognition remains unclear. Here, we use in vitro single-molecule imaging to directly visualize DNA loop extrusion and plasmid cleavage by Wadjet. We find that Wadjet is a symmetric DNA loop extruder that simultaneously reels in DNA from both sides of a growing loop and that this activity requires a dimeric JetABC supercomplex containing two dimers of the JetC motor subunit. On surface-anchored plasmid DNAs, Wadjet extrudes the full length of a 44 kilobase pair plasmid, stalls, and then cleaves DNA. Our findings reveal the role of loop extrusion in the specific recognition and elimination of plasmids by Wadjet, and establish loop extrusion as an evolutionarily conserved mechanism among SMC complexes across kingdoms of life., Competing Interests: Competing interest statement The authors declare no competing interests.