Strigolactone defective mutants ofArabidopsisexhibit delayed sepal senescence

Abstract

12 13 One-sentence summary: Two novel mutants in the strigolactone pathway demonstrate a role for 14 the hormone in sepal senescence, and transcriptional analysis highlights interaction between 15 strigolactones and sugar signalling. 16 17 Author contributions: 18 XX, PPD and DAH conceived and designed experiments; XX, RJ and AE did mutant screening; HB 19 oversaw transient expression, LCMS and QTOF analysis and XX, YW, LD and KF did the analysis; XX 20 and AM did statistics; XX and AH performed nCounter; AS generated figures for crystal structures. 21 HB and KF wrote LCMS and QTOF method sections. XX, PPD, and DAH wrote the manuscript. All 22 authors read and approved the manuscript. 23 24 Affiliations: 25 Abstract 32Flower sepals are critical for flower development and vary greatly in lifespan depending on their 33 function postpollination. However, very little is known on what controls sepal longevity. Using a 34 sepal senescence mutant screen, we directly connected strigolactones (SL) with sepal longevity. 35 We identified two Arabidopsis mutants that harbour novel mutations in the SL biosynthetic gene 36 MORE AXILLARY GROWTH1 (MAX1) and receptor DWARF14 (AtD14). The mutation in AtD14 caused 37 a substitution of the catalytic Ser-97 to Phe in the enzyme active site. The lesion in MAX1 changed 38 a highly conserved Gly-469 to Arg in the haem-iron ligand signature of the cytochrome P450 39 protein, which caused loss-of-function of MAX1. nCounter-based transcriptional analysis suggested 40 an interaction between SL and sugar signalling in controlling dark-induced inflorescence 41 senescence. The results uncover an important function for SL in regulating floral organ senescence 42 in addition to its other diverse functions in plant development and stress response. 43 44 2