Lemon Tree

Citrus thorny problem solved, according to ScienceDaily 18 June 2020, and Current Biology 18 June 2020; doi: 10.1016/j.cub.2020.05.068.

Thorns on citrus trees are well known to form when branches start to develop, but stop growing and become hard and dry, leaving a sharp spike.  Scientists at Yale University have now tracked down the genetic control of thorn formation in citrus.  Branches start to grow when cells called stem cells rapidly divide, producing new shoots and the shoots continue to grow as long as a protein named WUS stimulates the stem cells to keep dividing.  But when the WUS protein is no longer active the stem cells stop dividing and the newly formed shoots stop growing. 

Scientists were able to track down two growth control genes that turned WUS off. However, when they deliberately inactivated these two genes, the shoots continued to grow and sprout small leaves rather than forming thorns.  Researchers hope their finds will help breed citrus trees with more leaves and fruit-bearing branches.

Link: ScienceDaily

Editorial Comment: We have known for a long time that the type of thorns formed on citrus trees, and some other plants, are the result of developing branches ceasing to grow, so it is interesting to uncover the genetic basis of this process.  Normally the WUS protein is not turned off until the shoots need to stop growing and start forming flowers, which become fruit if they are fertilised.  The activity of the two genes found in this study causes the premature cessation of shoot growth, without activating other genes that would stimulate the shoots to sprout leaves or form flowers.  As such, their activity results in a degeneration, and maybe these genes have lost a connection they once had with the genes controlling growth of leaves and flowers. 

Evolutionists claim that thorns evolved to deter animals from eating the plants.  However, most browsing animals manage to avoid thorns, or are not bothered by them.  It is we human beings cultivating such plants who are most bothered by thorns.  Note well the Biblical position – the formation of thorns is actually the result of God’s curse on the earth when He judged Adam’s sin.  (Genesis 3:17-18)  See our article Biblical Thorns, PDF here.

Evidence News
5 August 2020
Creation Research Australia

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