YUCCA4 overexpression modulates auxin biosynthesis and transport and influences plant growth and development via crosstalk with abscisic acid in Arabidopsis thaliana

Abstract

Auxin regulates a plethora of events during plant growth and development, acting in concert with other phytohormones. YUCCA genes encode flavin monooxygenases that function in tryptophan-dependent auxin biosynthesis. To understand the contribution of the YUCCA4 (YUC4) gene on auxin homeostasis, plant growth and interaction with abscisic acid (ABA) signaling, 35S::YUC4 seedlings were generated, which showed elongated hypocotyls with hyponastic leaves and changes in root system architecture that correlate with enhanced auxin responsive gene expression. Differential expression of PIN1, 2, 3 and 7 auxin transporters was detected in roots of YUC4 overexpressing seedlings compared to the wild-type: PIN1 was down-regulated whereas PIN2, PIN3 and PIN7 were up-regulated. Noteworthy, 35S::YUC4 lines showed enhanced sensitivity to ABA on seed germination and postembryonic root growth, involving ABI4 transcription factor. The auxin reporter genes DR5::GUS, DR5::GFP and BA3::GUS further revealed that abscisic acid impairs auxin responses in 35S::YUC4 seedlings. Our results indicate that YUC4 overexpression influences several aspects of auxin homeostasis and reveal the critical roles of ABI4 during auxin-ABA interaction in germination and primary root growth.

Clathrin light chains regulate hypocotyl elongation by affecting the polarization of the auxin transporter PIN3 in Arabidopsis

“…These data support the importance of auxin synthesized in the shoot apex and cotyledons and the indispensable role of auxin transport during clathrin‐mediated hypocotyl elongation. Similarly, inhibition of auxin transport reduces YUCCA overexpression‐induced hypocotyl elongation, supporting the function of auxin transport in this process (Munguia‐Rodriguez et al, 2020).…”

“…Clathrin participates in numerous auxin‐regulated processes, including embryogenesis, root growth, and cell polarity and elongation (Chen et al, 2011; Kitakura et al, 2011; Mravec et al, 2011; Wang et al, 2013), which led us to focus on the function of auxin in clathrin‐mediated hypocotyl growth. Increased auxin biosynthesis and application of exogenous pro‐auxins enhance hypocotyl elongation (Smalle et al, 1997; Savaldi‐Goldstein et al, 2008; Challa et al, 2016; Munguia‐Rodriguez et al, 2020). Although transcription of the auxin biosynthesis‐related gene YUCCA8 increased, overall auxin content and TAA1 expression decreased in clc2‐1 clc3‐1 mutant hypocotyls compared to the wild type (Figure S2B).…”

“…The TAA/YUC (TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS/YUCCA)‐dependent route is the best understood auxin biosynthesis pathway so far (Won et al, 2011). TAA1 and YUCCAs affect hypocotyl elongation (Yamada et al, 2009; Munguia‐Rodriguez et al, 2020). For instance, overexpression of YUCCA4 contributes to an increased auxin level and therefore promotes hypocotyl growth; however, it is required for auxin to be transported to growth zones (Munguia‐Rodriguez et al, 2020), suggesting an indispensable role for auxin polar transport in hypocotyl elongation.…”

Interplay between Hormones and Several Abiotic Stress Conditions on Arabidopsis thaliana Primary Root Development

“…In addition, the loss of function mutant of AUXIN RESPONSE FACTOR 2 (ARF2) (arf2-101), an auxin transcription repressor that also acts as a negative regulator of ABA signaling, is hypersensitive to ABA and has shorter PRs, whereas the ARF2 OE has longer PRs than the mutant arf2-101, under ABA exogenous applications [143]. Furthermore, the OE of the auxin biosynthesis gene YUCCA 4 (YUC4) has shorter PRs than WT plants under ABA exogenous application [144] (Figure 2A and Table S2).…”

Abscisic Acid Regulates the Root Growth Trajectory by Reducing Auxin Transporter PIN2 Protein Levels in Arabidopsis thaliana

“…The relative intensities of Col-0, ABA and cyp707a1,3 represent the membrane intensities normalized to their original RFP intensities (post-conversion). -Rodriguez et al (2020) proved that excess auxin content may confer oversensitivity to root elongation induced by ABA; Thole et al (2014) had demonstrated that root elongation in both aux1 and pin2 is insensitive to ABA. These together demonstrated that ABA could affect root growth through modulating auxin transport, and is in line with our main conclusions that ABA regulates root growth trajectory via auxin transporter (PIN2; Figure 10).…”