Rahman Abidur, Nakasone Akari, Chhun Tory, Ooura Chiharu, Biswas Kamal Kanti, Uchimiya Hirofumi, Tsurumi Seiji, Baskin Tobias I, Tanaka Atsushi, Oono Yutaka
Research Group for Plant Resource Application, Japan Atomic Energy Research Institute, Takasaki 370-1292, Japan.
Plant J. 2006 Sep;47(5):788-801. doi: 10.1111/j.1365-313X.2006.02832.x.
2,4-dichlorophenoxyacetic acid (2,4-D), a chemical analogue of indole-3-acetic acid (IAA), is widely used as a growth regulator and exogenous source of auxin. Because 2,4-D evokes physiological and molecular responses similar to those evoked by IAA, it is believed that they share a common response pathway. Here, we show that a mutant, antiauxin resistant1 (aar1), identified in a screen for resistance to the anti-auxin p-chlorophenoxy-isobutyric acid (PCIB), is resistant to 2,4-D, yet nevertheless responds like the wild-type to IAA and 1-napthaleneacetic acid in root elongation and lateral root induction assays. That the aar1 mutation alters 2,4-D responsiveness specifically was confirmed by analysis of GUS expression in the DR5:GUS and HS:AXR3NT-GUS backgrounds, as well as by real-time PCR quantification of IAA11 expression. The two characterized aar1 alleles both harbor multi-gene deletions; however, 2,4-D responsiveness was restored by transformation with one of the genes missing in both alleles, and the 2,4-D-resistant phenotype was reproduced by decreasing the expression of the same gene in the wild-type using an RNAi construct. The gene encodes a small, acidic protein (SMAP1) with unknown function and present in plants, animals and invertebrates but not in fungi or prokaryotes. Taken together, these results suggest that SMAP1 is a regulatory component that mediates responses to 2,4-D, and that responses to 2,4-D and IAA are partially distinct.
2,4-二氯苯氧乙酸（2,4-D）是吲哚-3-乙酸（IAA）的化学类似物，被广泛用作生长调节剂和生长素的外源来源。由于2,4-D引发的生理和分子反应与IAA引发的反应相似，因此人们认为它们共享一条共同的反应途径。在此，我们表明，在筛选对抗生长素对氯苯氧异丁酸（PCIB）具有抗性的过程中鉴定出的一个突变体——抗生长素抗性1（aar1），对2,4-D具有抗性，但在根伸长和侧根诱导试验中，其对IAA和1-萘乙酸的反应仍与野生型相似。通过分析DR5:GUS和HS:AXR3NT-GUS背景下的GUS表达，以及通过实时PCR定量IAA11表达，证实了aar1突变特异性地改变了对2,4-D的反应性。两个已鉴定的aar1等位基因均存在多基因缺失；然而，通过用两个等位基因中缺失的一个基因进行转化，恢复了对2,4-D的反应性，并且通过使用RNAi构建体降低野生型中同一基因的表达，再现了对2,4-D的抗性表型。该基因编码一种功能未知的小酸性蛋白（SMAP1），存在于植物、动物和无脊椎动物中，但不存在于真菌或原核生物中。综上所述，这些结果表明SMAP1是介导对2,4-D反应的调节成分，并且对2,4-D和IAA的反应部分不同。
