Rocks may fall (thus the need for warning signs on highways), but leaves are pushed off of trees by a genetic program. The process, called abscission, has been mysterious for a long time. A team from the University of Missouri has mapped out, for the first time, the abscission pathway in one plant. Being this is the first day of fall, it would be worthwhile to think about the processes behind autumn’s colorful cascade of leaves. The opening paragraph in PNAS1 shows why leaf fall doesn’t just happen. Look at just a few of the processes involved:Abscission is a physiological process that involves the programmed separation of entire organs, such as leaves, petals, flowers, and fruit. Abscission allows plants to discard nonfunctional or infected organs, and promotes dispersion of progeny. At the cellular level, abscission is the hydrolysis of the middle lamella of an anatomically specialized cell layer, the abscission zone (AZ), by cell wall-modifying and hydrolyzing enzymes. Thus, abscission requires both the formation of the AZ early in the development of a plant organ and the subsequent activation of the cell separation response.Gene knockout experiments showed that proteins missing from a signalling cascade formed plants deficient in abscission ability. “A growing paradigm in signal transduction pathways,” they explained, “features receptor modules that perceive signals and modules such as MAPK cascades that relay and amplify this information to downstream effectors.” Because little is known about this signalling process, they studied it in the common lab plant Arabidopsis (a European/Asian herb also called thale cress). A press release about the study posted on PhysOrg was titled, “When leaves fall, more is occurring than a change of weather.” That can be illustrated by the researchers’ ending paragraph. It shows they uncovered the workings of only a small part of a very complex process:Multiple gene products, including potential signaling ligands, membrane receptors, protein kinase cascades, regulators of hormone responses, and transcription factors have been implicated in the regulation of abscission in plants. We have demonstrated, by several different lines of evidence, that there is a signaling cascade (Fig. 5B), from putative ligand (IDA) to receptors (HAE HSL2) to cytoplasmic effectors (MKK4, MKK5, MPK3, and MPK6), which function together to control cell separation during abscission. Additional gene products are also likely to play important roles in abscission and the relationships between them and the signaling pathway outlined here remain to be determined. However, based on the genetic interactions between IDA, HAE, HSL2, MKK4, and MKK5, it seems that this core signaling cascade is an important regulator of floral abscission.All this for something we take for granted this time of year: colorful leaves drifting by the window.1. Cho, Larue, Chevalier, Wang, Jinn, Zhang, and Walker, “Regulation of floral organ abscission in Arabidopsis thaliana,” Proceedings of the National Academy of Sciences USA, published online before print September 22, 2008, doi: 10.1073/pnas.0805539105.The autumn leaves drift by my window,The autumn leaves of red and gold;I dream of genes and MAPK modules,Of signal pathways yet scarcely told.When evolutionists continue to proclaim glib generalities about how plants evolved this and animals evolved that, it’s essential to look in detail at some of the structures and processes they’re talking about. Even something as common as leaf fall is not simple. The plant has to sense the time of year. It has to signal the nucleus to translate genes and produce the right proteins in the right quantities. These form a cascade of signals, with feedback loops, that instigate changes in cell adhesion. The right cells have to start separating in the right order. Simultaneously, the photosynthetic organs have to shut down. The changes in pigments have to be expressed to provide plant protection (10/27/2007). The stems have to weaken so the leaves will drop only when the plant has enough resources for the coming winter. These are just a few considerations behind the programmed, coordinated, environmentally-responsive genetic program devoted just to this one operation. The PhysOrg article tried to explain why leaves fall. “Aged leaves, for example, may be shed to facilitate the recycling of nutrients, ripening fruits dropped to promote seed dispersal and infected or diseased floral organs discarded to prevent the spread of disease.” Whoa… that’s teleology-talk. Stop right there on that first suggestion. How could a tree plan its own recycling program? After the leaves have dropped, the nutrients are gone. They’re lying on the ground. it doesn’t make any sense to say that the plant facilitated a recycling program, nor that it was trying to promote its own seed dispersal, or trying to prevent the spread of disease. The plant is a brainless machine programmed with these functions. If you don’t believe computers can emerge and program themselves, then plants cannot do such things, either. Such subtle personification fallacies are ubiquitous in evolutionary literature. Plants do these things because they were programmed to do them. Many questions remain. How does the whole plant know to change color all at once? Since abscission also relates to fruit and seed dispersal, how does the abscission program know when the seed ripening program has completed? How do the stems on maple seeds loosen at precisely the time when the seeds, that work like marvelous propellers in the wind, are ready to fly? Let’s teach our kids to see beyond the surface properties of nature into its marvelous secrets. This is good inoculation against dogmas that would have them believe complex programmed operations just happen. Suggested visual resources: Journey of Life and Wonders of God’s Creation from Moody Video, and Incredible Creatures that Defy Evolution from Exploration Films. Or, take a walk in the woods for a 360-degree, surround-sound demonstration.(Visited 20 times, 1 visits today)FacebookTwitterPinterestSave分享0
16 July 2014 Apartheid is gone, but the world still faces the threats of poverty, discrimination, climate change, conflict and more, United Nations Secretary-General Ban Ki-moon said on Tuesday. “Nelson Mandela Day is a call to action. Each of us can celebrate this day by helping to address real problems in our communities,” Ban said in a statement. “Together we can give great meaning to our celebration by paving the way for a better future.” The idea of Mandela Day was inspired by Mandela at his 90th birthday celebrations in London’s Hyde Park in 2008, when he said: “It is time for new hands to lift the burdens. It is in your hands now.” The United Nations officially declared 18 July as Nelson Mandela International Day in November 2009, recognising Mandela’s “values and his dedication to the service of humanity” and acknowledging his contribution “to the struggle for democracy internationally and the promotion of a culture of peace throughout the world”. Celebrated across the globe in honour of the late statesman’s birthday on 18 July, the day gives everyone the opportunity to emulate Mandela’s role as public servant. Individuals, groups and corporates are challenged to give 67 minutes of their time on the day – one minute for every year of Mandela’s public service – to take action to change the world for the better and, in doing so, to help build a global movement for good. On 22 June 1990 Mandela, newly freed from jail and then the deputy president of the African National Congress, addressed the Special Committee Against Apartheid in the UN General Assembly Hall in New York – the first time he had spoken at the UN. “Nelson Mandela’s presence in the General Assembly Hall proved that United Nations resolutions, sanctions and solidarity can win over violence and injustice,” Ban said on Tuesday. “His extraordinary compassion after 27 years in prison showed that human rights and equality are stronger than discrimination and hate. On that day in 1990, he said people would always be challenged by the fact that, quote, ‘it took as long as it has before all of us stood up to say enough is enough’. The room burst into applause.” SAinfo reporter
Don’t miss out on the latest news and information. Facing old rivals the Netherlands for the third time in six months, Germany enjoyed its revenge.The Dutch beat Germany 3-0 in Amsterdam in October and earned a last-gasp draw in the return fixture. Those results helped to relegate Germany from the top tier of the Nations League — further embarrassment after its disastrous 2018 World Cup campaign when it failed to advance from the group stage.Schulz’s winner came just when it looked like his team had let the Dutch salvage a draw from 2-0 down in the Group C game.“We didn’t control the ball and if you can’t exert pressure the game opens up and you see that they have some amazing attackers,” Netherlands coach Ronald Koeman said.Germany had gone six competitive games without a win since beating Sweden at the World Cup.ADVERTISEMENT “It’s good for the self-belief of this young team,” said Germany coach Joachim Loew. “I can live with criticism. I know what our potential is.”Croatia looked a shadow of the resilient team which reached the World Cup final in July as it lost 2-1 to Hungary in Budapest. Spells of confusion in the Croatian defense are likely to concern coach Zlatko Dalic in a group where four teams look like contenders for two qualifying spots for Euro 2020.FEATURED STORIESSPORTSPrivate companies step in to help SEA Games hostingSPORTSPalace wants Cayetano’s PHISGOC Foundation probed over corruption chargesSPORTSSingapore latest to raise issue on SEA Games food, logisticsElsewhere, Wales started with a tense win over Slovakia, while Belgium and Poland enjoyed comfortable victories.GERMANY’S REVENGE Houston moves into Sweet 16 for first time in 35 years Colombia protesters vow new strike after talks hit snag HAZARD’S CENTENARYOne hundred games for Belgium and Eden Hazard is still dangerous.Hazard scored his 30th career international goal in his centenary game as Belgium beat Cyprus 2-0 to tighten its grip on Group I. Michy Batshuayi finished with a goal and an assist as Belgium eased to a routine win to stay top of the group with six points.Valencia winger Denis Cheryshev scored two goals and set up another as Russia bounced back from its opening loss to Belgium on Thursday with a 4-0 dismantling of Kazakhstan.Still mourning last week’s loss to Kazakhstan, Scotland fans had little to celebrate as their team struggled to a 2-0 win over San Marino, the world’s lowest-ranked team. Scotland, which hasn’t qualified for a European Championship since 1996, is still guaranteed a playoff spot thanks to Nations League results.POLAND WINS AGAINPoland took control of Group G with a second straight win, beating Latvia 2-0, while Austria’s qualifying hopes are already looking in doubt.Latvia’s goalkeeper Pavels Steinbors made a string of spectacular saves before Robert Lewandowski broke the deadlock in the 76th minute with a header. Kamil Glik scored another header eight minutes later.Austria gave up a 1-0 lead as it lost 4-2 to Israel and is level with Latvia at the bottom of the group with no points from its opening two games. Eran Zahavi scored a hat trick as Israel earned its first win over Austria for 20 years.North Macedonia is level with Israel on four points after drawing 1-1 with Slovenia. Panelo: Duterte ‘angry’ with SEA Games hosting hassles Wintry storm delivers US travel woes before Thanksgiving View comments Google Philippines names new country director Germany’s Nico Schulz, fourth from left, celebrates with his teammates after scoring his side’s third goal during the Euro 2020 group C qualifying soccer match between Netherlands and Germany at the Johan Cruyff ArenA in Amsterdam, Sunday, March 24, 2019. (AP Photo/Peter Dejong)Germany is winning again, and Croatia is struggling. The World Cup feels like a long time ago.After a year of problems off the field — and humiliation on it — the new Germany is finally starting to look like the old Germany. Grit, determination and Nico Schulz’s 90th-minute winner earned the Germans a confidence-boosting 3-2 win over the Netherlands on Sunday in a European Championship qualifier.ADVERTISEMENT LATEST STORIES Bloomberg: US would benefit from more, not fewer, immigrants Cayetano: Senate, Drilon to be blamed for SEA Games mess Private companies step in to help SEA Games hosting The challenge now for Loew is to keep the momentum going — after all, the win over Sweden was seen at the time as a much-needed boost after a poor run. It proved a false dawn when Germany promptly lost to South Korea and spectacularly crashed out of the World Cup.Germany’s next opponent, Belarus, lost 2-1 to group leader Northern Ireland which won its second straight group game with an 87th-minute goal from substitute Josh Magennis.CROATIA CREAKINGEight months after reaching the World Cup final, Croatia is unexpectedly struggling.Croatia’s defense was at times overwhelmed by a spirited Hungary team, conceding one goal to a fine passing move masterminded by Balazs Dzsudzsak, and the other after panicky set-piece defending.Since losing the World Cup final to France, Croatia’s results have been wildly inconsistent.A 6-0 loss to Spain in the Nations League, a 3-2 win over Spain soon after and Thursday’s labored 2-1 win over Azerbaijan have highlighted Croatia’s moments of brilliance and its vulnerabilities after losing key players to international retirement and injury.Earlier in the same group, Daniel James’ first international goal gave Wales the lead after five minutes against Slovakia before holding on to win 1-0.“It was a perfect start,” Wales coach Ryan Giggs said, and he was full of praise for the 21-year-old James. “He is a talent, and when you have got that raw pace you are a threat at any level.”Croatia, Hungary, Wales and Slovakia are level on three points in Group E. 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Mike Dunlap, a little known but highly respected assistant coach with St. John’s, was hired Monday by Michael Jordan’s Charlotte Bobcats, the school said in a statement released early Tuesday morning.Dunlap is a surprise hire because he has spent most of his career at the collegiate level, and was not mentioned as one of the leading candidates by Bobcat executives, who said the search was narrowed down to Hall of Fame coach Jerry Sloan, Indiana assistant Brian Shaw and Lakers assistant Quin Snyder.After initial interviews with Charlotte executives Rod Higgins and Rich Cho, Shaw and Snyder were brought in last week to interview with Bobcats owner Michael Jordan.Sloan pulled himself out of the running last week, and after meeting with Shaw and Snyder, Jordan decided to re-open the field and brought Dunlap back in for an interview on Monday, sources say. Impressed, Jordan offered Dunlap the job.Cho told ESPN.com’s Andy Katz on Monday night that “a strong emphasis in player development was extremely high on our priority list,” in response to the Dunlap hire. Dunlap is known as a teacher of the game amid his peers in college and in the NBA.Dunlap, who is known to favor an up-tempo style of play, will replace Paul Silas, whose contract was not renewed after Charlotte finished with the worst winning percentage in NBA history this past season. The Bobcats were 7-59.