Overexpression of a BRASSINAZOLE RESISTANT 1 homolog attenuates drought tolerance by suppressing the expression of PLETHORA-LIKE 1 in Setaria italica

Two potential BRASSINAZOLE RESISTANT 1 (BZR1) homologs were downregulated by brassinosteroids(BRs) in Setaria italica roots.Functional analysis showed that BR regulates the dephosphorylation and nuclear localization of Si BZR1 and that Si BZR1 binds conserved BZR1-recognizing cis elements.In comparison with the wild type,Si BZR1-overexpressing S.italica seedlings were more sensitive to BR-inhibited primary root growth and drought stress,indicating that Si BZR1 is a positive regulator of BR signaling and a negative regulator of drought tolerance in S.italica.PLETHORA-LIKE 1 (Si PLT-L1) was found to be a direct target gene of Si BZR1 in S.italica roots.The expression of Si PLT-L1 was downregulated by Si BZR1.Si PLT-L1-overexpressing S.italica was less sensitive to BR-inhibited root growth and more tolerant to drought stress,possibly owing to the upregulation of drought-inducible Dehydrin-family genes.

Brassinosteroids regulate outer ovule integument growth in part via the control of INNER NO OUTER by BRASSINOZOLE‐RESISTANT family transcription factors

Brassinosteroids(BRs)play important roles in regulating plant reproductive processes.BR signaling or BR biosynthesis null mutants do not produce seeds under natural conditions,but the molecular mechanism underlying this infertility is poorly understood.In this study,we report that outer integument growth and embryo sac development were impaired in the ovules of the Arabidopsis thaliana BR receptor null mutant bri1-116.Gene expression and RNA-seq analyses showed that the expression of INNER NO OUTER(INO),an essential regulator of outer integument growth,was significantly reduced in the bri1-116 mutant.Increased INO expression due to overexpression or increased transcriptional activity of BRASSINAZOLE-RESISTANT 1(BZR1)in the mutant alleviated the outer integument growth defect in bri1-116 ovules,suggesting that BRs regulate outer integument growth partially via BZR1-mediated transcriptional regulation of INO.Meanwhile,INO expression in bzr-h,a null mutant for all BZR1 family genes,was barely detectable;and the outer integument of bzr-h ovules had much more severe growth defects than those of the bri1-116 mutant.Together,our findings establish a new role for BRs in regulating ovule development and suggest that BZR1 family transcription factors might regulate outer integument growth through both BRI1-dependent and BRI1-independent pathways.

Recent selection and introgression facilitated high-altitude adaptation in cattle

During the past 3000 years,cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia,ultraviolet(UV)radiation,and extreme cold.The genetic mechanism underlying this rapid adaptation is not yet well understood.Here,we present whole-genome resequencing data for 258 cattle from 32 cattle breeds/populations,including 89 Tibetan cattle representing eight populations distributed at altitudes ranging from 3400 m to 4300 m.Our genomic analysis revealed that Tibetan cattle exhibited a continuous phylogeographic cline from the East Asian taurine to the South Asian indicine ancestries.We found that recently selected genes in Tibetan cattle were related to body size(HMGA2 and NCAPG)and energy expenditure(DUOXA2).We identified signals of sympatric introgression from yak into Tibetan cattle at different altitudes,covering 0.64%–3.26%of their genomes,which included introgressed genes responsible for hypoxia response(EGLN1),cold adaptation(LRP11),DNA damage repair(LATS1),and UV radiation resistance(GNPAT).We observed that introgressed yak alleles were associated with noncoding variants,including those in present EGLN1.In Tibetan cattle,three yak introgressed SNPs in the EGLN1 promoter region reduced the expression of EGLN1,suggesting that these genomic variants enhance hypoxia tolerance.Taken together,our results indicated complex adaptation processes in Tibetan cattle,where recently selected genes and introgressed yak alleles jointly facilitated rapid adaptation to high-altitude environments.