BYPASS1: How a Tiny Mutant Tells a Big Story about Root‐to‐shoot Signaling

Abstract

Plants coordinate their development using long-distance signaling. The vascular system provides a route for long-distance movement, and specifically the xylem for root-to-shoot signaling. Root-toshoot signals play roles communicating soil conditions, and these signals are important for agricultural water conservation. Using genetic approaches, the Arabidopsis bypass1 (bps1) mutant, which over-produces a root-derived signal, was identified. Although bps1 mutants have both root and shoot defects, the shoot can develop normally if the roots are removed, and the mutant root is sufficient to induce arrest of the wild-type shoot. BYPASS1 encodes a protein with no functionally characterized domains, and BPS1-like genes are found in plant genomes, but not the genomes of animals. Analyses of hormone pathways indicate that the mobile compound that arises in bps1 roots requires carotenoid biosynthesis, but it is neither abscisic acid nor strigolactone. The current model suggests that BPS1 is required to prevent the synthesis of a novel substance that moves from the root to the shoot, where it modifies shoot growth by interfering with auxin signaling.Sieburth LE, Lee DK (2010) BYPASS1: How a tiny mutant tells a big story about root-to-shoot signaling.

Ethylene Responses in Rice Roots and Coleoptiles Are Differentially Regulated by a Carotenoid Isomerase-Mediated Abscisic Acid Pathway

“…Field-grown mhz5 plants under environmental light conditions did not resemble wild-type plants, suggesting that light can only partially substitute for MHZ5/CRTISO activity, which is consistent with previous reports in Arabidopsis and tomato (Isaacson et al, 2002;Park et al, 2002). In addition to the current roles of the carotenoid-derived ABA pathway in the regulation of rice seedling growth, other carotenoid-derived molecules, e.g., SL, BYPASS, and uncharacterized compounds, may be responsible for tiller formation (Supplemental Figure 1), root development (Supplemental Figure 2), and other phenotypic changes in fieldgrown mhz5 plants (Nambara and Marion-Poll, 2005;Umehara et al, 2008;Sieburth and Lee, 2010;Kapulnik et al, 2011;Puig et al, 2012;Ramel et al, 2012;Van Norman et al, 2014).…”

“…Carotenoid-derived compounds, such as SL, ABA, BYPASS, b-cyclocitral, and other uncharacterized molecules, modulate plant developmental processes and stress responses in many organs (Xie et al, 2010;Sieburth and Lee, 2010;Walter et al, 2010;Cazzonelli and Pogson, 2010;Puig et al, 2012;Ramel et al, 2012;Avendaño-Vázquez et al, 2014;Van Norman et al, 2014;Liu et al, 2015). The regulation of carotenoid biosynthesis is interconnected with plant developmental and environmental responses, and the biosynthesis pathway is regulated at both the transcriptional and posttranscriptional levels in plants ( Ruiz-Sola and Rodríguez-Concepción, 2012).…”

Overexpression of the OsERF71 Transcription Factor Alters Rice Root Structure and Drought Resistance

“…The plant organs to detect drought stress conditions are roots, and upon drought perception, they release signals to induce resistance and/or adapt their architecture for optimal growth under these conditions (Sieburth and Lee, 2010;Atkinson and Urwin, 2012). Split-root experiments in drought conditions and drought-inducible maize (Zea mays) root signals indicate that roots generate uncharacterized droughtinducible signals that move to the aerial parts of the plant and confer drought resistance to the shoots (Went, 1943;Passioura, 1988;Saab and Sharp, 1989;Gowing et al, 1990;Chazen and Neumann, 1994).…”

Plant Vascular Biology and Agriculture

“…The pioneering studies of Fritz Went (1943) revealed the involvement of root‐derived signals that appeared to regulate growth of the vegetative regions of the plant. The roles of these signals in water use efficiency, control over shoot branching and overall shoot growth are reviewed in this Special Issue by Sieburth and Lee (2010). The identification of a novel protein, BYPASS1, is discussed with respect to its function in interdicting the synthesis of a novel root‐to‐shoot signal; this molecule may well be a branch product of the carotenoid biosynthetic pathway.…”