Plant roots are constantly exposed to a variety of abiotic stresses, and high salinity is one of the major limiting conditions that impose constraints on plant growth. In this study, we describe that OsMADS25 is required for the root growth as well as salinity tolerance, via maintaining ROS homeostasis in rice (Oryza sativa). Overexpression of OsMADS25 remarkably enhanced the primary root (PR) length and lateral root (LR) density, whereas RNAi silence of this gene reduced PR elongation significantly, with altered ROS accumulation in the root tip. Transcriptional activation assays indicated that OsMADS25 activates OsGST4 (glutathione S–transferase) expression directly by binding to its promoter. Meanwhile, osgst4 mutant exhibited repressed growth and high sensitivity to salinity and oxidative stress, and recombinant OsGST4 protein was found to have ROS–scavenging activity in vitro. Expectedly, overexpression of OsMADS25 significantly enhanced the tolerance to salinity and oxidative stress in rice plants, with the elevated activity of antioxidant enzymes, increased accumulation of osmoprotective solute proline and reduced frequency of open stoma. Furthermore, OsMADS25 specifically activated the transcription of OsP5CR, a key component of proline biosynthesis, by binding to its promoter. Interestingly, overexpression of OsMADS25 raised the root sensitivity to exogenous ABA, and the expression of ABA–dependent stress–responsive genes was elevated greatly in overexpression plants under salinity stress. In addition, OsMADS25 seemed to promote auxin signaling by activating OsYUC4 transcription. Taken together, our findings reveal that OsMADS25 might be an important transcriptional regulator that regulates the root growth and confers salinity tolerance in rice via the ABA–mediated regulatory pathway and ROS scavenging.
Background
The MADS-box transcription factors mainly function in floral organ organogenesis and identity specification. Few research on their roles in vegetative growth has been reported.
Results
Here we investigated the functions of
OsMADS57
in plant vegetative growth in rice (
Oryza sativa
). Knockdown of
OsMADS57
reduced the plant height, internode elongation and panicle exsertion in rice plants. Further study showed that the cell length was remarkably reduced in the uppermost internode in
OsMADS57
knockdown plants at maturity. Moreover,
OsMADS57
knockdown plants were more sensitive to gibberellic acid (GA
3
), and contained less bioactive GA
3
than wild-type plants, which implied that
OsMADS57
is involved in gibberellin (GA) pathway. Expectedly, the transcript levels of
OsGA2ox3
, encoding GAs deactivated enzyme, were significantly enhanced in
OsMADS57
knockdown plants. The level of
EUI1
transcripts involved in GA deactivation was also increased in
OsMADS57
knockdown plants. More importantly, dual-luciferase reporter assay and electrophoretic mobility shift assay showed that OsMADS57 directly regulates the transcription of
OsGA2ox3
as well as
EUI1
through binding to the CArG-box motifs in their promoter regions. In addition, OsMADS57 also modulated the expression of multiple genes involved in GA metabolism or GA signaling pathway, indicating the key and complex regulatory role of OsMADS57 in GA pathway in rice.
Conclusions
These results indicated that OsMADS57 acts as an important transcriptional regulator that regulates stem elongation and panicle exsertion in rice via GA-mediated regulatory pathway.
Electronic supplementary material
The online version of this article (10.1186/s12284-019-0298-6) contains supplementary material, which is available to authorized users.
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