Abstract
Proline plays a crucial role in the drought stress response in plants. However, there are still gaps in our knowledge about the molecular mechanisms that regulate proline metabolism under drought stress. Here, we report that the histone methylase encoded by CAU1, which is genetically upstream of P5CS1 (encoding the proline biosynthetic enzyme Δ1-pyrroline-5-carboxylate synthetase 1), plays a crucial role in proline-mediated drought tolerance. We determined that the transcript level of CAU1 decreased while that of ANAC055 (encoding a transcription factor) increased in wild-type Arabidopsis under drought stress. Further analyses showed that CAU1 bound to the promoter of ANAC055 and suppressed its expression via H4R3sme2-type histone methylation in the promoter region. Thus, under drought stress, a decreased level of CAU1 led to an increased transcript level of ANAC055, which induced the expression of P5CS1 and increased proline level independently of CAS. Drought tolerance and the level of proline were found to be decreased in the cau1 anac055 double-mutant, while proline supplementation restored drought sensitivity in the anac055 mutant. Our results reveal the details of a novel pathway leading to drought tolerance mediated by CAU1.
Highlights
In plants under osmotic stress, proline is mainly synthesized by P5CS (Δ1-pyrroline-5-carboxylate synthetase) (Savouré et al, 1995; Yoshiba et al, 1995; Székely et al, 2008) and P5CR (P5C reductase) from glutamate in chloroplasts (Szoke et al, 1992; Verbruggen et al, 1993)
We report that the histone methylase encoded by CAU1, which is genetically upstream of P5CS1, plays a crucial role in proline-mediated drought tolerance
These results indicated that the ANAC055 level was enhanced in cau1, and that drought stress suppressed CAU1 expression but increased ANAC055 expression
Summary
In plants under osmotic stress, proline is mainly synthesized by P5CS (Δ1-pyrroline-5-carboxylate synthetase) (Savouré et al, 1995; Yoshiba et al, 1995; Székely et al, 2008) and P5CR (P5C reductase) from glutamate in chloroplasts (Szoke et al, 1992; Verbruggen et al, 1993). Several studies have shown that the transcription of P5CS1 is activated by H2O2-derived signals, the calcium signal, PLC (phospholipase C), PLD (phospholipase D), and by the ABAdependent pathway (Yoshiba et al, 1995; Savouré et al, 1997; Strizhov et al, 1997; Parre et al, 2007; Verslues et al, 2007; Ghars et al, 2008). ABI1 (ABA-INSENSITIVE 1) and the CaM4 calmodulin-MYB2 regulatory pathway are involved in the control of P5CS1 transcription (Knight et al, 1997; Strizhov et al, 1997; Yoo et al, 2005; Parre et al, 2007). Much is known about the biological functions of proline in stress tolerance, its regulation needs further investigation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
