Establishment of symbiosis between nitrogen-fixing rhizobia and legume plants depends on lipochitoligosaccharides, called Nod factors. These bacterial nodulation signals are rapidly hydrolyzed by host enzymes. Cai et al. (pages 397–414) have identified a symbiotic function for such a Nod factor cleaving enzyme (MEDICAGO TRUNCATULA NOD FACTOR HYDROLASE1 [MtNFH1]). MtNFH1 plays a role in the fine-tuning of the symbiosis at the stage of rhizobial root infection and in nitrogen-fixing nodules. M. truncatula mutant plants deficient in MtNFH1 display delayed rhizobial root hair infection, nodule hypertrophy, and abnormal nodule branching. Such nodule branching was also observed for wild-type plants inoculated by a Nod factor overproducing Sinorhizobium meliloti strain. The cover image depicts clustered nodules formed on roots of the MtNFH1-deficient mutant nfh1-3 (20 d postinoculation with S. meliloti wild-type bacteria).
新植物学家：西北农林揭示H2S信号对拟南芥根系发育的调控
Hydrogen sulfide (H2S) 是一种内源气态信号物质，参与植物生长发育，并与其它激素存在功能上的关联。本研究发现，H2S可以对cytokinin oxidase/dehydrogenases (CKXs) 成员之一CKX2的 (Cys)62 进行Persulfidation的翻译后修饰，导致其酶活水平提高，从而提降低了细胞分裂素的水平，导致根系构型发生变化。借助转基因株系和突变体株系，作者证实H2S影响了根系对重力信号的反应，缩短根毛，增加了侧根的数目。
此外，H2S还影响了侧根的伸长区域。
小结：本研究解释了H2S 通过翻译后激活CKX2，进而影响根系发育的机制。
The model of H2S regulating root system architecture (RSA) through persulfidation. H2S positively regulates cytokinin oxidase/dehydrogenase (CKX2) activity through the persulfidation of CKX2Cys62, thereby reducing cytokinin (CTK) content, and leading to changes in Arabidopsis RSA. The specific performance is smaller gravitropic set-point angle (GSA), fewer root hairs, and more LRs.
原文：Hydrogen sulfide antagonizes cytokinin to change root system architecture through persulfidation of CKX2 in Arabidopsis
