AtMYBS1 negatively regulates heat tolerance by directly repressing the expression of MAX1 required for strigolactone biosynthesis in Arabidopsis

Heat stress caused by global warming requires the development of thermotolerant crops to sustain yield.It is necessary to understand the molecular mechanisms that underlie heat tolerance in plants.Strigolactones(SLs)are a class of carotenoid-derived phytohormones that regulate plant development and responses to abiotic or biotic stresses.Although SL biosynthesis and signaling processes are well established,genes that directly regulate SL biosynthesis have rarely been reported.Here,we report that the MYB-like transcription factor AtMYBS1/AtMYBL,whose gene expression is repressed by heat stress,functions as a negative regulator of heat tolerance by directly inhibiting SL biosynthesis in Arabidopsis.Overexpression of AtMYBS1 led to heat hypersensitivity,whereas atmybs1 mutants displayed increased heat tolerance.Expression of MAX1,a critical enzyme in SL biosynthesis,was induced by heat stress and downregulated in AtMYBS1-overexpression(OE)plants but upregulated in atmybs1 mutants.Overexpression of MAX1 in the AtMYBS1-OE background reversed the heat hypersensitivity of AtMYBS1-OE plants.Loss of MAX1 function in the atmyb1 background reversed the heat-tolerant phenotypes of atmyb1 mutants.Yeast one-hybrid assays,chromatin immunoprecipitation‒qPCR,and transgenic analyses demonstrated that AtMYBS1 directly represses MAX1 expression through the MYB binding site in the MAX1 promoter in vivo.The atmybs1d14 double mutant,like d14 mutants,exhibited hypersensitivity to heat stress,indicating the necessary role of SL signaling in AtMYBS1-regulated heat tolerance.Our findings provide new insights into the regulatory network of SL biosynthesis,facilitating the breeding of heat-tolerant crops to improve crop production in a warming world.

Analysis of differential expression of genes induced by ethephon in elongating internodes of maize plants

Plant growth regulators(PGRs) are commonly used in cereal cropping systems to restrict plant height and control lodging. Ethephon has been reported to shorten internodes and increase grain yield of maize. To analyze the transcriptomic profiles of maize internode elongation following ethephon treatment, differentially expressed genes were compared between the treatment and contro samples of inbred line Zong 31 using the Affymetrix Maize Genome Array. According to the microarray data 326 probe sets showed significant change in expression Further research revealed that the most remarkable effects of ethephon on maize internodes elongation occurred during a 48 h period, when 89 differentially expressed genes were detected. There were dramatic change in transcript levels at 24 h and six Auxin transport genes and four gibberellin biosynthesis pathway genes were differentially expressed in Zong 31 in response to ethephon treatment. In summary, we showed that gaseous ethylene release is involved in internode meristem cell elongation through the regulation of plant hormone signaling in maize. This work provides a platform for studies in which candidate genes will be functionally tested for involvement in internode elongation.