The cyclin‐dependent kinase G group defines a thermo‐sensitive alternative splicing circuit modulating the expression of ArabidopsisATU2AF65A

Abstract

SummaryThe ability to adapt growth and development to temperature variations is crucial to generate plant varieties resilient to predicted temperature changes. However, the mechanisms underlying plant response to progressive increases in temperature have just started to be elucidated. Here, we report that the cyclin‐dependent kinase G1 (CDKG1) is a central element in a thermo‐sensitive mRNA splicing cascade that transduces changes in ambient temperature into differential expression of the fundamental spliceosome component, ATU2AF65A. CDKG1 is alternatively spliced in a temperature‐dependent manner. We found that this process is partly dependent on both the cyclin‐dependent kinase G2 (CDKG2) and the interacting co‐factor CYCLIN L1 (CYCL1), resulting in two distinct messenger RNAs. The relative abundance of both CDKG1 transcripts correlates with ambient temperature and possibly with different expression levels of the associated protein isoforms. Both CDKG1 alternative transcripts are necessary to fully complement the expression of ATU2AF65A across the temperature range. Our data support a previously unidentified temperature‐dependent mechanism based on the alternative splicing (AS) of CDKG1 and regulated by CDKG2 and CYCL1. We propose that changes in ambient temperature affect the relative abundance of CDKG1 transcripts, and this in turn translates into differential CDKG1 protein expression coordinating the AS of ATU2AF65A.

Thermo-Sensitive Alternative Splicing of FLOWERING LOCUS M Is Modulated by Cyclin-Dependent Kinase G2

“…The wild type Columbia (Col-0) and mutant stocks cdkg1-1 (SALK_075762), cdkg2-1 (SALK_012428), and cycL1-1 (SAIL_285_G10) used in this study were obtained from the Nottingham Arabidopsis Stock Centre and have previously been described (Zheng et al, 2014;Ma et al, 2015;Cavallari et al, 2018).…”

“…CDKC, for instance is part of the positive transcription elongation factor b (P-TEFb) that phosphorylates the C-terminal domain of RNA polymerase II (PolII) (Cui et al, 2007), modulates the localization of spliceosome components (Kitsios et al, 2008) and can regulates flowering time through promoting expression of an FLC antisense transcript called COOLAIR (Wang et al, 2014). The CDKG group is the most closely related to mammalian CDKs (Menges et al, 2005;Umeda, 2005) that are involved in mRNA processing (Bartkowiak et al, 2010;Chen et al, 2006;Loyer et al, 2005;Even et al, 2006) and have been also shown to regulate splicing (Huang et al, 2013;Cavallari et al, 2018), meiosis (Zheng et al, 2014) and flowering responses (Ma et al, 2015).…”

“…In Arabidopsis, two closely related genes, CDKG1 and CDKG2, encode for the catalytic subunit of the kinase, which physically interacts with the regulatory subunit, CYCLIN L1 (CYCL1) (Van Leene et al, 2010). CDKG1, CDKG2, and CYCL1 have a role in mRNA splicing (Xu et al, 2012;Huang et al, 2013) forming part of an ambient temperature responsive AS cascade targeting genes involved in splicing (Cavallari et al, 2018). Moreover, CDKG1 is required for chromosome pairing and recombination at high ambient temperature (Zheng et al, 2014) while CDKG2 was reported as a negative regulator of flowering (Ma et al, 2015) although the molecular pathway involved was not identified.…”

CDKG1 Is Required for Meiotic and Somatic Recombination Intermediate Processing in Arabidopsis

“…In addition to its meiotic role, it is clear that CDKG1 also has wider functions including the role in promoting somatic DNA repair by homologous recombination described here. Moreover, CDKG1 affects splicing in somatic tissues (Cavallari et al, 2018), and in anthers, the loss of CDKG1 results in the incorrect splicing of the callose synthase gene CalS5, impaired callose synthesis and abnormal pollen cell wall formation (Huang et al, 2013). This likely contributes to the low seed set observed in cdkg1-1 mutants, despite a relatively modest reduction in bivalent number.…”

Double Crossed: CDKG1 Regulates Crossover Formation by Stabilizing Meiotic and Somatic Recombination Intermediates

“…Finally, CDKG1 was also found-like other major genes regulating recombination, such as FANCMto play an important role in somatic DNA repair. Other studies have found that CDKG1 is involved in temperaturespecific splicing cascades (Cavallari et al, 2018), stimulating speculation regarding the possible mechanism by which it may act. Thus, further work on the molecular mechanisms by which CDKG1 regulates meiotic proteins might reveal additional facets of an important protein.…”