BAK1 plays contrasting roles in regulating abscisic acid-induced stomatal closure and abscisic acid-inhibited primary root growth in Arabidopsis

The mechanisms that balance plant growth and stress responses are poorly understood, but they appear to involve abscisic acid(ABA) signaling mediated by protein kinases. Here, to explore these mechanisms, we examined the responses of Arabidopsis thaliana protein kinase mutants to ABA treatment. We found that mutants of BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE 1(BAK1) were hypersensitive to the effects of ABA on both seed germination and primary root growth. The kinase OPEN STOMATA 1(OST1) was more highly activated by ABA in bak1 mutant than the wild type. BAK1 was not activated by ABA treatment in the dominant negative mutant abi1-1 or the pyr1 pyl4 pyl5 pyl8 quadruple mutant, but it was more highly activated by this treatment in the abi1-2 abi2-2 hab1-1 loss-of-function triple mutant than the wild type. BAK1 phosphorylates OST1 T146 and inhibits its activity. Genetic analyses suggested that BAK1 acts at or upstream of core components in the ABA signaling pathway, including PYLs, PP2 Cs,and Sn RK2 s, during seed germination and primary root growth. Although the upstream brassinosteroid(BR) signaling components BAK1 and BR INSENSITIVE 1(BRI1) positively regulate ABAinduced stomatal closure, mutations affecting downstream components of BR signaling, including BRASSINOSTEROID-SIGNALING KINASEs(BSKs)and BRASSINOSTEROID-INSENSITIVE 2(BIN2), did not affect ABA-mediated stomatal movement. Thus,our study uncovered an important role of BAK1 in negatively regulating ABA signaling during seed germination and primary root growth, but positively modulating ABA-induced stomatal closure, thus optimizing the plant growth under drought stress.

Measuring BGP AS Path Looping(BAPL) and Private AS Number Leaking(PANL)

As a path vector protocol, Border Gateway Protocol （BGP） messages contain an entire Autonomous System （AS） path to each destination for breaking arbitrary long AS path loops. However, after observing the global routing data from RouteViews, we find that BGP AS Path Looping （BAPL） behavior does occur and in fact can lead to multi-AS forwarding loops in both IPv4 and IPv6. The number and ratio of BAPLs in IPv4 and IPv6 on a daily basis from August 1,2011 to August 31, 2015 are analyzed. Moreover, the distribution of BAPLs among duration and loop length in IPv4 and IPv6 are also studied. Several possible explanations for BAPL are discussed in this paper. Private AS Number Leaking （PANL） has contributed to 0.20% of BAPLs in IPv4, and at least 1.76% of BAPLs in IPv4 were attributed to faulty configurations and malicious attacks. Valid explanations, including networks of multinational companies, preventing particular AS from accepting routes, also can lead to BAPLs. Motivated by the large number of PANLs that contribute to BAPLs, we also study the number and the ratio of PANLs per day in the 1492 days. The distribution of the private AS numbers in all of the PANLs is concentrated, and most of them are located in the source of the AS paths. The majority of BAPLs resulted from PANLs endure less than one day, and the number of BAPLs which are caused by two or more leaked private ASes are much larger than that of BAPLs which are caused by one leaked private AS. We explain for this phenomenon and give some advices for the operators of ASes.

Interest-suppression-based NDN live video broadcasting over wireless LAN

Named data networking （NDN） is a new Internet architecture that replaces today＇s focus on where - addresses and hosts with what -- the content that users and applications care about. One of NDN＇s prominent advantages is scalable and efficient content distribution due to its native support of caching and multicast in the network. However, at the last hop to wireless users, often the WiFi link, current NDN im- plementation still treats the communication as multiple uni- cast sessions, which will cause duplicate packets and waste of bandwidth when multiple users request for the same popular content. WiFi＇s built-in broadcast mechanism can alleviate this problem, but it suffers from packet loss since there is no MAC-layer acknowledgement as in unicast. In this paper, we develop a new NDN-based cross-layer approach called NLB for efficient and scalable live video streaming over wireless LAN. The core ideas are： using WiFi＇s broadcast channel to deliver content from the access point to the users, a leader- based mechanism to suppress duplicate requests from users, and receiver-driven rate control and loss recovery. The design is implemented and evaluated in a physical testbed comprised of one software AP and 20 Raspberry Pi-based WiFi clients. While NDN with multiple unicast sessions or plain broadcast can support no more than ten concurrent viewers of a 1Mbps streaming video, NDN plus NLB supports all 20 viewers, and can likely support much more when present.