番茄SlIAMT1和SlIAMT2的表达及其对下胚轴和根生长的调控

doi:10.16420/j.issn.0513-353x.2020-1063

摘要/Abstract

摘要：

从‘Ailsa Craig’番茄中克隆到两个IAA甲基转移酶（indole-3-acetic acid methyltransferase,IAMT）基因SlIAMT1和SlIAMT2,其全长分别为2 510和4 620 bp,均编码390个氨基酸。序列分析表明,二者均具有IAA甲基转移酶特异的底物结合位点和催化位点,与拟南芥AtIAMT1的序列相似度高于70%。利用PlantCARE数据库进行启动子顺式作用元件预测分析发现,SlIAMT1和SlIAMT2启动子序列中含有与生长素（IAA）、脱落酸（ABA）、水杨酸（SA）及光信号响应相关的顺式作用元件。荧光定量PCR分析表明,SlIAMT1在番茄萌发的种子、幼苗根、新叶以及青果中有优势表达,而SlIAMT2则主要在花蕾中表达。诱导表达分析表明,番茄幼苗中,尤其是下胚轴中,SlIAMT1的表达受强光照（150 μmol · m^-2· s^-1）强烈诱导,而SlIAMT2受光照诱导程度较低;15 ℃低温处理对SlIAMT1和SlIAMT2的诱导程度均较低;IAA处理可显著诱导SlIAMT1和SlIAMT2的表达;ABA诱导根和下胚轴中SlIAMT1的表达,但抑制子叶中的SlIAMT1的表达,并抑制根中SlIAMT2的表达;SA抑制根和子叶中SlIAMT1的表达,但对子叶中SlIAMT2的表达有一定的诱导作用。异源转化结果显示,拟南芥iamt1缺失突变体下胚轴和主根长于野生型,突变体中过量表达SlIAMT1可有效恢复下胚轴和主根的表型;进一步分析表明,SlIAMT1过量表达显著降低了拟南芥幼苗侧根对IAA的敏感性。试验结果表明,SlIAMT响应光和激素信号,通过IAA甲基化修饰调节IAA稳态,调控幼苗下胚轴和根系发育。

关键词: 番茄, IAA甲基转移酶, 表达分析, 根系, 下胚轴

Abstract:

Two indole-3-acetic acid methyltransferase（IAMT）genes,SlIAMT1 and SlIAMT2,were cloned from tomato cultivar‘Ailsa Craig’. The full-length of SlIAMT1 and SlIAMT2 genes were 2 510 and 4 620 bp,respectively,and both of them encode 390 amino acids. The sequence alignment suggested that both SlIAMT1 and SlIAMT2 contained all of the substrate binding sites and catalytic sites for IAMT,and showed more than 70% sequence identity with AtIAMT1 from Arabidopsis. In silico analysis suggested that the promoter sequences of SlIAMT1 and SlIAMT2 contained several typical cis-acting elements,including auxin-,abscisic acid-,salicylic acid- and light-responsive elements by using PlantCARE databases. Real-time PCR assays showed that SlIAMT1 was highly expressed in the germinating seeds,roots of 5-d-old seedlings,young leaves and green fruits,while SlIAMT2 was extensively expressed in the flower buds. In tomato seedlings,the expression of SlIAMT1 was remarkably induced by high light intensity（150 μmol · m^-2 · s^-1）,especially in the hypocotyls. However,the inducible level of SlIAMT2 was much lower. The induction of SlIAMT1 and SlIAMT2 was low by low temperature（15 ℃）treatment. IAA also exerted inducible effects on SlIAMT1 and SlIAMT2 expression. ABA induced the expression of SlIAMT1 in root and hypocotyl,but repressed its expression in cotyledons,while for SlIAMT2,its expression was repressed by ABA in root. SA repressed the expression of SlIAMT1 in roots and cotyledons,but slightly induced SlIAMT2 expression in cotyledons. The function of SlIAMT1 gene was further investigated by Agrobacterium-mediated genetic transformation into Arabidopsis. The iamt1 mutant showed longer hypocotyl and primary roots than wild type,and these phenotypes of mutant were functionally complemented by overexpression of SlIAMT1. Overexpression of SlIAMT1 could also reduce the sensitivity to IAA in lateral roots. These results indicated that SlIAMT genes respond to light and hormone signals,and regulate the IAA homeostasis via methylation and thereby regulate the hypocotyl and root development.

Key words: Solanum lycopersicum, IAMT, expression analysis, root, hypocotyl

中图分类号:

S641.2

张静亚, 雷蕾, 尚庆茂, 谢露露, 董春娟. 番茄SlIAMT1和SlIAMT2的表达及其对下胚轴和根生长的调控[J]. 园艺学报, 2021, 48(12): 2385-2402.

ZHANG Jingya, LEI Lei, SHANG Qingmao, XIE Lulu, DONG Chunjuan. Expression Patterns of Tomato SlIAMT1 and SlIAMT2 and Their Functions During Hypocotyl and Root Development[J]. Acta Horticulturae Sinica, 2021, 48(12): 2385-2402.

图/表 14

表1 本研究中所用的引物

Table 1 Primers used in this study

用途Use	基因Gene	引物序列（5′-3′）Sequence
基因克隆 Gene clone	SlIAMT1	F：CACTAGCAAAACAATAGAGACA;R：TCTAATACATGAGAGACATATAGACTT
基因克隆 Gene clone	SlIAMT2	F：TCTACTTTTATGGTTAGATTCTG;R：TATCCCAAATGTTGCTTAA
qRT-PCR	SlIAMT1	F：CTCAAGCTCAGGGGCAACAT;R：ATCTCCGGCGAGTTTAGCTG
	SlIAMT2	F：CTCAAGCCCAGGGACAACAT;R：CGAAGGGGATGTCGTCGTTAT
	SlActin41	F：CTTCCAGCAGATGTGGATTGC;R：GCATCTCTGGTCCAGTAGGAAA
	AtIAMT1	F：CGGTCTACTCTTCGGCACTC;R：GGTGCGTACACCGGGATATT
	AtActin2	F：ACACTGTGCCAATCTACGAGGGTT;R：ACAATTTCCCGCTCTGCTGTTGTG
载体构建 Transgenic vector construction	35S:SlIAMT1	F：CGGTACCCGGGGATCCATGGCACCTTTAGGAGACAA; R：CGACTCTAGAGGATCCCTACACAAGAGAAAGTGAAGCAACA

图1 光照和黑暗条件下外源MeIAA处理对番茄幼苗下胚轴和根系生长的影响不同小写字母表示相同培养条件下差异显著（P < 0.05）。

Fig. 1 Effects of exogenous MeIAA application on growth of hypocotyls and roots in tomato seedlings under light and dark conditions Different lowercases indicate significant differences between groups under same culture condition（P < 0.05）.

表2 SlIAMT1和SlIAMT2基因的序列特征

Table 2 Sequence characteristics of SlIAMT1 and SlIAMT2 genes in tomato

基因 Gene	序列号 Accession No.	基因全长/bp Gene length	外显子数 Number of exons	内含子数 Number of introns	ORF/ bp	蛋白长度/aa Protein length	分子量/ kD MW	等电点 pI	亚细胞定位 Subcellular localization
SlIAMT1	Solyc07G064990	2 510	4	3	1 173	390	42.92	5.58	细胞质Cytoplasm
SlIAMT2	Solyc12G014500	4 620	4	3	1 173	390	43.28	5.90	细胞质Cytoplasm

图2 SlIAMT1和SlIAMT2与拟南芥AtIAMT1蛋白序列的同源比对 ▼：SAM/SAH结合位点;*：与IAA羧基的作用位点;†：与IAA芳香基团的作用位点。

Fig. 2 Homology alignment of SlIAMT1 and SlIAMT2 with Arabidopsis AtIAMT1 protein sequences ▼：SAM/SAH-binding site;*：Interaction site with carboxyl moiety of IAA;†：Interaction site with aromatic moiety of IAA.

图3 番茄SlIAMT蛋白与其他植物IAMT蛋白的系统进化树

Fig. 3 Phylogenetic tree of SlIAMT proteins and IAMTs from other plant species

表3 SlIAMT1和SlIAMT2启动子重要顺式作用元件

Table 3 Some important cis-acting regulatory elements in the promoters of SlIAMT1 and SlIAMT2

调控元件 Cis-element	核心序列 Core sequence	元件功能描述 Functional description of cis-element	位置Positions^*
调控元件 Cis-element	核心序列 Core sequence	元件功能描述 Functional description of cis-element	SlIAMT1	SlIAMT2
ABRE	CACGTG	ABA响应元件 cis-Acting element involved in the abscisic acid responsiveness	-1 547	-552、 -1 129、 -1 921
TCA-element	CCATCTTTTT	水杨酸响应元件 cis-Acting element involved in salicylic acid responsiveness	-1 513	/
TGA-element	AACGAC	生长素响应元件 Auxin-responsive element	/	-791
TGACG-motif	TGACG	茉莉酸甲酯响应元件 cis-Acting regulatory element involved in the methyl jasmonate responsiveness	/	-367
MBS	CAACTG	参与干旱诱导的MYB结合位点 MYB binding site involved in drought-inducibility	/	-712
ACE	CTAACGTATT	光响应元件cis-Acting element for light responsive	-1 754	/
G-box	TACGTG	光响应元件cis-Acting element for light responsive	-1 546,-1 981	/
GT1-motif	GGTTAA	光响应元件Light responsive element	-263,-170, -1 500,-1 810	/
AE-box	AGAAACAA	光响应元件的一部分 Part of a module for light response	-1 867	/
AT1-motif	AATTATTTTTTATT	光响应元件的一部分 Part of a light responsive module	-1 711、-698	/
I-box	TGATAATGT	光响应元件的一部分 Part of a light responsive element	-1 331	/
MRE	AACCTAA	参与光响应的MYB结合位点 MYB binding site for light responsive	/	-1 614、 -1 079

图4 番茄组织中SlIAMT1和SlIAMT2的表达不同小写字母表示不同组织间差异显著（P < 0.05）。

Fig. 4 Expression levels of SlIAMT1 and SlIAMT2 in different tissues of tomato The different lowercases indicate significant differences between groups（P < 0.05）.

图5 番茄幼苗根、下胚轴和子叶中SlIAMT1 和SlIAMT2对强光照（150 μmol · m-2 · s-1）的响应不同小写字母表示处理间差异显著（P < 0.05）。

Fig. 5 Expression levels of SlIAMT1 and SlIAMT2 in root,hypocotyl,and cotyledon of tomato seedlings in response to high light intensity（150 μmol · m-2 · s -1 Different lowercases indicate significant differences between groups（P < 0.05）.

图6 番茄幼苗根、下胚轴和子叶中SlIAMT1和SlIAMT2对低温（15 ℃/15 ℃）的响应不同小写字母表示处理间差异显著（P < 0.05）。

Fig. 6 Expression levels of SlIAMT1 and SlIAMT2 in root,hypocotyl,and cotyledon of tomato seedlings in response to low temperature（15 ℃/15 ℃） Different lowercases indicate significant differences between groups（P < 0.05）.

图7 番茄幼苗根、下胚轴和子叶中SlIAMT1 和SlIAMT2对IAA的响应不同小写字母表示处理间差异显著（P < 0.05）。

Fig. 7 Expression levels of SlIAMT1 and SlIAMT2 in root,hypocotyl,and cotyledonof tomato seedlings in response to IAA Different lowercases indicate significant differences between groups（P < 0.05）.

图8 番茄幼苗根、下胚轴和子叶中SlIAMT1 和SlIAMT2对ABA的响应不同小写字母表示处理间差异显著（P < 0.05）。

Fig. 8 Expression levels of SlIAMT1 and SlIAMT2 in root,hypocotyl,and cotyledon of tomato seedlings in response to ABA Different lowercases indicate significant differences between groups（P < 0.05）.

图9 番茄幼苗根、下胚轴和子叶中SlIAMT1和SlIAMT2对SA的响应不同小写字母表示处理间差异显著（P < 0.05）。

Fig. 9 Expression levels of SlIAMT1 and SlIAMT2 in root,hypocotyl,and cotyledon of tomato seedlings in response to SA Different lowercases indicate significant differences between groups（P < 0.05）.

图10 SlIAMT1过量表达对拟南芥iamt1突变体幼苗下胚轴和根系生长的影响不同小写字母表示差异显著（P < 0.05）。

Fig. 10 Effects of SlIAMT1 overexpression on hypocotyl and root growth in Arabidopsis iamt1 mutant Different lowercases indicate significant differences between groups（P < 0.05）.

图11 SlIAMT1过量表达对拟南芥iamt1突变体幼苗响应IAA的影响 IAA浓度是取lg后的值。**、***分别表示在0.01和0.001水平差异显著。

Fig. 11 Effects of overexpression of SlIAMT1 on the response of Arabidopsis iamt1 mutant seedlings to IAA The concentration of IAA is the logarithmic value. **,*** indicate significant differences between groups at 0.01 and 0.001 level,respectively.

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