माप संयंत्र सेल दीवार एक्सटेंशन (क्रीप) अम्लीय pH और अल्फा Expansin द्वारा प्रेरित
Summary
हम एक निरंतर बल एक्सटेन्सोमीटर का उपयोग करने के लिए संयंत्र सेल की दीवार नमूनों की लंबी अवधि के विस्तार (रेंगना) अम्लीय buffers और expansin प्रोटीन से प्रेरित उपाय प्रदर्शित करता है.
Abstract
Growing plant cell walls characteristically exhibit a property known as ‘acid growth’, by which we mean they are more extensible at low pH (< 5) 1. The plant hormone auxin rapidly stimulates cell elongation in young stems and similar tissues at least in part by an acid-growth mechanism 2, 3. Auxin activates a H+ pump in the plasma membrane, causing acidification of the cell wall solution. Wall acidification activates expansins, which are endogenous cell wall-loosening proteins 4, causing the cell wall to yield to the wall tensions created by cell turgor pressure. As a result, the cell begins to enlarge rapidly. This ‘acid growth’ phenomenon is readily measured in isolated (nonliving) cell wall specimens. The ability of cell walls to undergo acid-induced extension is not simply the result of the structural arrangement of the cell wall polysaccharides (e.g. pectins), but depends on the activity of expansins 5. Expansins do not have any known enzymatic activity and the only way to assay for expansin activity is to measure their induction of cell wall extension. This video report details the sources and preparation techniques for obtaining suitable wall materials for expansin assays and goes on to show acid-induced extension and expansin-induced extension of wall samples prepared from growing cucumber hypocotyls.
To obtain suitable cell wall samples, cucumber seedlings are grown in the dark, the hypocotyls are cut and frozen at -80 °C. Frozen hypocotyls are abraded, flattened, and then clamped at constant tension in a special cuvette for extensometer measurements. To measure acid-induced extension, the walls are initially buffered at neutral pH, resulting in low activity of expansins that are components of the native cell walls. Upon buffer exchange to acidic pH, expansins are activated and the cell walls extend rapidly. We also demonstrate expansin activity in a reconstitution assay. For this part, we use a brief heat treatment to denature the native expansins in the cell wall samples. These inactivated cell walls do not extend even in acidic buffer, but addition of expansins to the cell walls rapidly restores their ability to extend.
Protocol
Discussion
इस प्रदर्शन के लिए हम ककड़ी hypocotyls से सेल दीवारों का उपयोग किया है क्योंकि वे दीवार के नमूने है कि संभाल करने के लिए और है कि अच्छी संवेदनशीलता के साथ जवाब के लिए आसान कर रहे हैं एक विश्वसनीय स्रोत हो साबित …
Acknowledgements
यहाँ दिखाया तकनीकों धन के साथ ऊर्जा विभाग (Bioenergy विज्ञान) और राष्ट्रीय विज्ञान फाउंडेशन से अनुदान द्वारा विकसित किए गए.
References
- Cosgrove, D. J. Characterization of long-term extension of isolated cell walls from growing cucumber hypocotyls. Planta. 177, 121-130 (1989).
- Rayle, D. L., Cleland, R. E. The Acid Growth Theory of auxin-induced cell elongation is alive and well. Plant Physiol. 99, 1271-1274 (1992).
- Cleland, R. E. Auxin-induced growth of Avena coleoptiles involves two mechanisms with different pH optima. Plant Physiol. 99, 1556-1561 (1992).
- Cosgrove, D. J. Loosening of plant cell walls by expansins. Nature. 407, 321-326 (2000).
- McQueen-Mason, S., Durachko, D. M., Cosgrove, D. J. Two endogenous proteins that induce cell wall expansion in plants. Plant Cell. 4, 1425-1433 (1992).
