PYR/PYL receptors play a major role for regulation of transcriptional response to abscisic acid. Arabidopsis thaliana

Abscisic acid (ABA) is a key hormone for plant growth, development and stress adaptation. Perception of ABA through four types of receptors has been reported. We show here that impairment of ABA perception through the PYR/PYL/RCAR branch reduces vegetative growth and seed production, and leads to a severely open stomata and dramatic ABA insensitive phenotype, even though other branches for ABA perception remain functional. Arabidopsis sextuple mutant impaired in 6 PYR/PYL receptors, namely PYR1, PYL1, PYL2, PYL4, PYL5 and PYL8, was able to germinate and grow even on 100 mM ABA. Whole-rosette stomatal conductance (Gst) measurements revealed that leaf transpiration in the sextuple pyr/pyl mutant was higher than in the ABA-deficient aba3-1 or ABA-insensitive snrk2.6 mutants. The gradually increasing Gst values of plants lacking three, four, five and six PYR/PYLs indicate quantitative regulation of stomatal aperture by this family of receptors. The sextuple mutant lacked ABA-mediated activation of SnRK2s and ABA-responsive gene expression was dramatically impaired as was reported in snrk2.2/2.3/2.6. In summary, these results show that ABA perception by PYR/PYLs plays a major role to regulate seed germination and establishment, basal ABA signaling required for vegetative and reproductive growth, stomatal aperture and transcriptional response to the hormone. Overall design: Four biological replicates were generated for the 3 genotypes, pyr1pyl1pyl2pyl4pyl5pyl8 sextuple mutant, snrk2.2/2.3/2.6 triple mutant, and Col-0. All the samples were treated with ABA for 3 hours before harvesting. The four Col-0 samples were mix to create an unique reference Col-0 sample. Two comparasion were made, fisrt one, PYR/PYL sextuple mutant versus Col-0 reference sample and second one, SnRK2 triple mutant versus Col-0 reference sample. In each comparasion four biological replicates were made. Replicas number 1 and 2 were labeled with Cy5 for the mutant sample and Cy3 for the Col-0 reference sample, while the other two replicas,#3 and #4, were reversed-labeled.

脱落酸（Abscisic acid, ABA）是调控植物生长、发育与逆境适应的关键激素。已有研究表明，ABA可通过四类受体实现感知。本研究证实，阻断PYR/PYL/RCAR通路的ABA感知功能，会抑制植物营养生长与种子产量，并导致气孔严重开放以及显著的ABA不敏感表型，即便其他ABA感知通路仍保持正常功能。拟南芥中6个PYR/PYL受体（PYR1、PYL1、PYL2、PYL4、PYL5与PYL8）功能缺失的六重突变体，即便在100 mM ABA培养基上仍可正常萌发与生长。整株莲座气孔导度（stomatal conductance, Gst）测定结果显示，该六重pyr/pyl突变体的叶片蒸腾速率高于ABA缺失型aba3-1突变体与ABA不敏感型snrk2.2/2.3/2.6突变体。随着缺失PYR/PYL受体的数量依次增加（3、4、5、6个），植株的气孔导度逐渐升高，表明该受体家族对气孔开度具有定量调控作用。该六重突变体无法介导ABA对SnRK2激酶的激活，且ABA响应基因的表达受到显著抑制，这与snrk2.2/2.3/2.6突变体的表型一致。综上，上述结果表明，PYR/PYL家族介导的ABA感知在调控种子萌发与建成、营养与生殖生长所需的基础ABA信号通路、气孔开度以及激素的转录响应中发挥核心作用。总体实验设计：针对3种基因型——pyr1pyl1pyl2pyl4pyl5pyl8六重突变体、snrk2.2/2.3/2.6三重突变体以及Col-0野生型，各设置4次生物学重复。所有样本在收获前均用ABA处理3小时。将4份Col-0样本混合，制备为统一的Col-0参考样本。本实验设置两组比较：第一组为PYR/PYL六重突变体与Col-0参考样本，第二组为SnRK2三重突变体与Col-0参考样本。每组比较均包含4次生物学重复：其中重复1与2采用Cy5标记突变体样本、Cy3标记Col-0参考样本；重复3与4则采用反向标记（即Cy5标记Col-0参考样本、Cy3标记突变体样本）。