Abstract
We reported earlier that 7B-1 mutant in tomato (Solanum lycopersicum L., cv. Rutgers), an ABA overproducer, is defective in blue light (B) signaling leading to B-specific resistance to abiotic and biotic stresses. Using a methylation-sensitive amplified polymorphism (MSAP) assay, a number of genes were identified, which were differentially methylated between 7B-1 and its wild type (WT) seedlings in white (W), blue (B), red (R) lights and dark (D) or in response to exogenous ABA and mannitol-induced stresses. The genomic methylation level was almost similar in different lights between 7B-1 and WT seedlings, while significant differences were observed in response to stresses in D, but not B. Using a cDNA-AFLP assay, several transcripts were identified, which were differentially regulated between 7B-1 and WT by B or D or in response to stresses. Blue light receptors cryptochrome 1 and 2 (CRY1 and CRY2) and phototropin 1 and 2 (PHOT1 and PHOT2) were not affected by the 7B-1 mutation at the transcriptional level, instead the mutation had likely affected downstream components of the light signaling pathway. 5-azacytidine (5-azaC) induced DNA hypomethylation, inhibited stem elongation and differentially regulated the expression of a number of genes in 7B-1. In addition, it was shown that mir167 and mir390 were tightly linked to auxin signaling pathway in 5-azaC-treated 7B-1 seedlings via the regulation of auxin-response factor (ARF) transcripts. Our data showed that DNA methylation remodeling is an active epigenetic response to different lights and stresses in 7B-1 and WT, and highlighted the differences in epigenetic and transcriptional regulation of light and stress responses between 7B-1 and WT. Furthermore, it shed lights on the crosstalk between DNA hypomethylation and miRNA regulation of ARFs expression. This information could also be used as a benchmark for future studies of male-sterility in other crops.
Highlights
IntroductionRutgers) is a genic photoperioddependent male-sterile in long days with stamens that are shrunken and produce non-viable
The main objective of this study was to investigate the differences in DNA methylation and transcriptional regulation in response to different lights and stresses between 7B-1 and wild type (WT), which were associated with the 7B-1 mutation and male-sterility in 7B-1
Despite some minor changes, expressions of CRY1/2, and PHOT1/2 were not significantly affected by 5-azaC in 7B-1 and WT, while hypocotyl 5 (HY5) strongly down regulated in 7B-1, but not WT. These results indicated that blue light receptors were not affected by the induced DNA hypomethylation and 5-azaC-induced inhibition of hypocotyl elongation in 7B-1 is independent and not regulated by CRY1/2 and HY5
Summary
Rutgers) is a genic photoperioddependent male-sterile in long days with stamens that are shrunken and produce non-viable. DNA Methylation and Transcriptomic Changes in 7B-1 Male-Sterile Tomato microspores [1], while in short days flowers are fertile and produce normal stamens and viable pollens. Compared to the WT, 7B-1 is less sensitive to light-induced inhibition (i.e., deetiolation) of hypocotyl growth, has a higher endogenous ABA level, but less GAs, IAA, CKs and is more tolerant to various abiotic stresses, specially under blue light [3,4,5]. A study by Fellner and Sawhney [4] suggested a defect in blue light perception in 7B-1, which in turn affected hormonal sensitivity and their endogenous level. Being a photoperiod-dependent male sterile and stress tolerant, the 7B-1 mutant offers an exceptionally attractive germplasm for hybrid tomato breeding [6]
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