CAREER: How SFR2 allows chloroplast envelope membranes to survive freezing, from initial signal to molecular mechanism.

预计天气不稳定程度将会上升，并威胁到作物产量。具体地说，反季节霜冻损害农作物，每年造成数十亿美元的损失，并限制生长季节，以避免潜在的霜冻可能造成数百亿美元的损失。同样重要的是，全球人口预计将会增加，在同样的土地上种植更多作物的需求迫在眉睫。对耐寒机制的认识不足限制了更耐寒作物的发展。该项目最终将提供新的知识，指导设计作物耐寒性的策略。已知有一种名为“对冰冻敏感2”(SFr2)的酶通过改变叶绿体膜的组成成分来帮助植物在冰冻中存活。虽然SFr2的S作用是已知的，但SFr2被激活以应对冰冻条件的方式以及它的行动提供优势的方式只是假设。这个项目使用遗传学、生物化学和生物物理方法的独特组合来检验这些假说。预计这些结果将立即加强培育耐寒作物的努力，并将影响其他物种和工程系统中膜温度稳定性的研究。在整个项目中，内布拉斯加州博士后研究人员和研究生在植物科学方面的培训将得到改进，以包括公共传播和其他融合技能。在这样做的过程中，内布拉斯加州的普通公众也将受益。一种名为对冷冻敏感2(SFr2)的酶通过减少单半乳脂和增加寡半乳脂来重塑叶绿体被膜。表达SFr2催化失活点突变体的植物比野生型植物更容易受冻。来自研究人员实验室的最新证据表明，SFr2在冷冻过程中通过细胞质酸化而被激活。在SFr2不活跃的其他逆境中，细胞质也会发生酸化。这一数据和其他数据表明，SFr2的活性与更全球化的细胞对冰冻温度的反应有关，在这种反应中，SFr2通过改变叶绿体被膜的物理性质来直接稳定其被膜。该项目将通过以下目标来验证这一假设：(1)确定SFr2依赖的脂类变化如何影响膜的稳定性。(2)确定SFr2活性是否受到翻译后修饰的抑制。(3)明确叶绿体被膜冷冻稳定机制的多样性。这些目标确定了在冰冻温度下允许膜完整性的机制，并定义了它们如何工作(Obj.1、Obj.3)，它们定义了一个关键的细胞冻结信号(Obj.2)。最后，他们还将提供对叶绿体被膜稳定机制的全面了解，这些机制在多个领域中有用。以下培训和科学素养目标与上述研究相结合：(4)为下一代科学家提供全面培训，使其成为有效的研究人员和传播者。(5)通过创新的图形小说和互动演示，教育和参与公众对植物科学的社会影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Weather instability is predicted to be on the rise and it threatens crop yields. Specifically, out-of-season frosts damage crops costing billions of dollars annually, and restricting growing seasons to avoid potential frosts likely costs in the tens of billions. Also important, the global population is expected to rise and the need to grow more crops on the same land is immediate. Poor understanding of freezing tolerance mechanisms constrains development of more tolerant crops. This project will ultimately provide new knowledge that can guide strategies to engineer freezing tolerance in crop plants. An enzyme named "Sensitive to Freezing 2" (SFR2) is known to help plants survive freezing by changing the building blocks of chloroplast membranes. Although SFR2's action is known, the way that SFR2 is activated to respond to freezing conditions and the way that its actions provide an advantage are only hypothesized. This project tests the hypotheses using a unique blend of genetics, biochemistry, and biophysical approaches. It is expected that the results will immediately enhance efforts to generate cold-tolerant crops and will also impact research on membrane temperature stability in other species and engineering systems. Throughout the project, training of Nebraskan post-doctoral researchers and graduate students in plant science will be improved to include public communication and other convergent skillsets. In doing so, members of the general public in Nebraska will also benefit.An enzyme known as Sensitive to Freezing 2 (SFR2) remodels the chloroplast envelope membranes by reducing monogalactolipids and increasing oligogalactolipids. Plants expressing catalytically inactive point mutants of SFR2 are more susceptible to freezing than wildtype plants. Recent evidence from the investigator's lab indicates that SFR2 is activated during freezing by cytoplasmic acidification. Acidification of the cytoplasm also occurs during other stresses in which SFR2 is not active. This and other data suggest that SFR2 activity is tied to a more global cellular response to freezing temperatures in which it directly stabilizes the chloroplast envelope membranes by altering their physical properties. This project will test this hypothesis through the following objectives: (1) Define how membrane stability is affected by SFR2-dependent changes to lipids. (2) Determine if SFR2 activity is repressed by post-translational modification. (3) Define the diversity of chloroplast envelope membrane freezing stabilization mechanisms. These objectives identify mechanisms allowing membrane integrity during freezing temperatures and define how they work (Obj. 1, Obj. 3), and they define a critical cellular freezing signal (Obj. 2). Finally, they will also provide a comprehensive understanding of chloroplast envelope stabilization mechanisms useful in multiple fields. The following training and science literacy objectives are integrated with the above research: (4) Provide comprehensive training for next-generation scientists to be effective researchers and communicators. (5) Educate and engage the public on the societal impact of plant science with innovative graphic novels and interactive presentations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.