銅で種子のサヤを破裂させる(Copper makes seed pods explode)

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破裂する種子のサヤの機械的構造を制御する遺伝子を特定 Researchers identify the genes controlling the mechanical structure of exploding seed pods

2022-06-07 マックス・プランク研究所

A stiff polymer called lignin (stained red) is deposited in a precise pattern in the cell walls of exploding seed pods. Researchers identified three laccase enzymes required to form this lignin. No lignin forms in the cell wall (stained blue) when all three genes are knocked out by CRISPR/Cas9 gene editing.A stiff polymer called lignin (stained red) is deposited in a precise pattern in the cell walls of exploding seed pods. Researchers identified three laccase enzymes required to form this lignin. No lignin forms in the cell wall (stained blue) when all three genes are knocked out by CRISPR/Cas9 gene editing.
© Miguel Pérez Antón

植物は、種子を広く普及させるために、さまざまな戦略をとってきた。風に乗って種子を撒くものもあれば、動物や鳥に種子の詰まった果実を食べてもらうよう誘惑するものもある。また、ポッピング・クレス(Cardamine hirsuta)のように、種子を四方八方に飛ばす爆発的な種子のさやを進化させた珍しい植物もある。ドイツ・ケルンのマックス・プランク植物育種研究所のAngela Hay教授らは、『PNAS』に掲載されたこの新しい研究で、どの遺伝子がこれらの爆発する種子のさやの機械的構造を制御しているのかを調査した。その結果、重要な微量栄養素である銅が、種子のさやにリグニンの正確なパターンを敷き詰めるのに必須であることが明らかになった。リグニンは、植物の主要な構造材料であるリグノセルロースに豊富に含まれる植物性高分子である。植物の細胞壁に存在し、木材を硬くする役割を担っている。

<関連情報>

爆発的な種子散布は、ラッカーゼを介したリグニンの局所的な沈着に十分な銅を確保するためにSPL7に依存する Explosive seed dispersal depends on SPL7 to ensure sufficient copper for localized lignin deposition via laccases

Miguel Pérez-Antón , Ilsa Schneider, Patrizia Kroll, Hugo Hofhuis, Sabine , Markus Pauly and Angela Hay
PNAS  Published:June 6, 2022
DOI:https://doi.org/10.1073/pnas.2202287119

Abstract

Exploding seed pods evolved in the Arabidopsis relative Cardamine hirsuta via morphomechanical innovations that allow the storage and rapid release of elastic energy. Asymmetric lignin deposition within endocarpb cell walls is one such innovation that is required for explosive seed dispersal and evolved in association with the trait. However, the genetic control of this novel lignin pattern is unknown. Here, we identify three lignin-polymerizing laccases, LAC4, 11, and 17, that precisely colocalize with, and are redundantly required for, asymmetric lignification of endocarpb cells. By screening for C. hirsuta mutants with less lignified fruit valves, we found that loss of function of the transcription factor gene SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 7 (SPL7) caused a reduction in endocarpb cell-wall lignification and a consequent reduction in seed dispersal range. SPL7 is a conserved regulator of copper homeostasis and is both necessary and sufficient for copper to accumulate in the fruit. Laccases are copper-requiring enzymes. We discovered that laccase activity in endocarpb cell walls depends on the SPL7 pathway to acclimate to copper deficiency and provide sufficient copper for lignin polymerization. Hence, SPL7 links mineral nutrition to efficient dispersal of the next generation.

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