Fu Minjie, Kang Hyun Kyung, Son Seung-Hyun, Kim Seong-Ki, Nam Kyoung Hee
Department of Life Systems, Sookmyung Women's University, Seoul 140-742, Korea These authors contributed equally to this article.
Department of Biological Sciences, Sookmyung Women's University, Seoul 140-742, Korea These authors contributed equally to this article.
Plant Cell Physiol. 2014 Nov;55(11):1892-904. doi: 10.1093/pcp/pcu118. Epub 2014 Sep 3.
Arabidopsis RAV1, RAV1L and RAV2/TEM2 are Related to ABI3/VP1 (RAV) transcription factors that contain both plant-specific B3 and AP2 domains. RAV1 was known to be a negative regulator of growth and its transcript level was repressed by brassinolide (BL). In this study, we found that the expressions of RAV1, and its closest homologs RAV1L and RAV2 were also regulated by other plant hormones, and especially repressed significantly by BL and abscisic acid (ABA), which mediate various abiotic stress responses in plants. Therefore, to further investigate the physiological functions of RAV1, RAV1L and RAV2 in abiotic stress responses, we isolated T-DNA insertional knockout mutants of each gene and produced transgenic plants overexpressing the RAVs. Under normal conditions, each single mutant showed slightly promoted growth patterns only at an early stage of development. In comparison, the RAV1-overexpressing plants exhibited strong growth retardation with semi-dwarfed stature. In drought conditions, RAVs-overexpressing transgenic plants exhibited higher transpirational water loss than the wild type. In salt conditions, seed germination of the RAVs-overexpressing transgenic plants was more inhibited than that of the wild type, while ravs mutants showed promoted seed germination. We also found that RAVs expressions were reduced by dryness and salt. RAV1-overexpressing plants showed the same patterns of increased expression as stress-inducible genes such as RD29A, RD29B and the genes encoding ABA biosynthetic enzymes, as did the wild type and rav1 mutant. However, the RAV1-overexpressing transgenic plants were insensitive to ABA, regardless of the higher accumulation of ABA even in normal conditions. Taken together, these results suggest that RAVs are versatile negative regulators for growth and abiotic stresses, drought and salt, and that negative regulatory effects of RAVs on abiotic stresses are likely to be operated independently of ABA.
拟南芥RAV1、RAV1L和RAV2/TEM2属于与ABI3/VP1相关的（RAV）转录因子，它们同时含有植物特有的B3和AP2结构域。已知RAV1是生长的负调控因子，其转录水平受油菜素内酯（BL）抑制。在本研究中，我们发现RAV1及其最接近的同源物RAV1L和RAV2的表达也受其他植物激素调控，尤其是显著受BL和脱落酸（ABA）抑制，而BL和ABA介导植物中的各种非生物胁迫反应。因此，为了进一步研究RAV1、RAV1L和RAV2在非生物胁迫反应中的生理功能，我们分离了每个基因的T-DNA插入敲除突变体，并培育了过表达RAV的转基因植物。在正常条件下，每个单突变体仅在发育早期表现出轻微的生长促进模式。相比之下，过表达RAV1的植物表现出强烈的生长迟缓，植株半矮化。在干旱条件下，过表达RAV的转基因植物比野生型表现出更高的蒸腾失水。在盐胁迫条件下，过表达RAV的转基因植物的种子萌发比野生型受到更强烈的抑制，而ravs突变体的种子萌发则得到促进。我们还发现，干旱和盐胁迫会降低RAV的表达。过表达RAV1的植物与野生型和rav1突变体一样，表现出与胁迫诱导基因（如RD29A、RD29B以及编码ABA生物合成酶的基因）相同的表达增加模式。然而，即使在正常条件下ABA积累较高，过表达RAV1的转基因植物对ABA也不敏感。综上所述，这些结果表明RAV是生长以及干旱和盐等非生物胁迫的多功能负调控因子，并且RAV对非生物胁迫的负调控作用可能独立于ABA发挥作用。
