Shen Ni

Plants coordinate their growth and developmental programs through dynamic communication in the core of the nucleus, enabling them to adapt to persistently high-temperature environments. Upon heat stress, plants primarily perceive and transduce thermal signals between the nucleus and other organelles, a process defined as nuclear-organellar communication. The published research on plants in response to heat environments mainly focuses on sensing heat physical signals from the plasma membrane (PM)/cytosol to the nucleus, eliciting nuclear transcriptional reprogramming and decoding organelle-derived retrograde signals to the nucleus. Consequently, plants have evolved sophisticated systems to decode adverse temperature signals relying on efficient nuclear-organellar coordination. This review summarizes how plants maintain cellular homeostasis via nuclear crosstalk. Heat signals are initially perceived, which triggers the production of secondary messengers including phosphatidic acid (PA), calcium ions (Ca²⁺) and reactive oxygen species (ROS). In addition, proteins also deliver thermal signals to the nucleus. As the central signaling hub, the nucleus orchestrates global transcriptional reprogramming predominantly through the Heat Shock Transcriptional Factors (HSFs)–heat shock proteins (HSPs) regulatory module, and sends instructions to the endoplasmic reticulum (ER), chloroplasts and mitochondria. Conversely, organelle-derived retrograde signals coordinate stress adaptation: the unfolded protein response relieves ER stress, and heat stress activates ROS-mediated chloroplast-to-nucleus and mitochondria-to-nucleus feedback pathways. We further outline candidate thermosensing proteins residing in different organelles, and highlight major unsolved issues. Critical knowledge gaps include the intrinsic thermosensing capacity of chloroplasts and mitochondria, inter-organellar coordination of second-messenger dynamics, specific organelle functions, and the biological roles of membrane contact sites. Further mechanistic insights will facilitate the application of genome editing, synthetic biology and artificial-intelligence-aided design to breed heat-tolerant crops without yield penalties.

Anther length is the critical floral trait determining hybrid rice seed production and is controlled by many quantitative trait loci (QTL). However, the cloning of genes specifically controlling anther size has yet to be reported. Here, we report the fine mapping of qAL5.2 for anther size using backcross inbred lines (BILs) in the genetic background of Oryza sativa indica Huazhan (HZ). Gene chip analysis on the BC₄F₂ and BC₅F₁ population identified effective loci on Chr1, Chr5, and Chr8 and two genomic regions on Chr5, named qAL5.1 and qAL5.2. qAL5.2 was identified in both populations with LOD values of 17.54 and 10.19, which explained 35.73% and 25.1% of the phenotypic variances, respectively. Ultimately qAL5.2 was localized to a 73 kb region between HK139 and HK140 on chromosome 5. And we constructed two near-isogenic lines (NILs) for RNA-seq analysis, named NIL-qAL5.2^HZ and NIL-qAL5.2^KLY, respectively. The result of the GO enrichment analysis revealed that differential genes were significantly enriched in the carbohydrate metabolic process, extracellular region, and nucleic acid binding transcription, and KEGG enrichment analysis revealed that alpha-linolenic acid metabolism was significantly enriched. Meanwhile, candidate genes of qAL5.2 were analyzed in RNA-seq, and it was found that ORF8 is differentially expressed between NIL-qAL5.2^HZ and NIL-qAL5.2^KLY. The fine mapping of qAL5.2 conferring anther length will promote the breed improvement of the restorer line and understanding of the mechanisms driving crop mating patterns.

Gibberellins (GAs) are diterpenoid phytohormones regulating various aspects of plant growth and development, such as internode elongation and seed germination. Although the GA biosynthesis pathways have been identified, the transcriptional regulatory network of GA homeostasis still remains elusive. Here, we report the functional characterization of a GA-inducible OsABF1 in GA biosynthesis underpinning plant height and seed germination. Overexpression of OsABF1 produced a typical GA-deficient phenotype with semi-dwarf and retarded seed germination. Meanwhile, the phenotypes could be rescued by exogenous GA₃, suggesting that OsABF1 is a key regulator of GA homeostasis. OsABF1 could directly suppress the transcription of green revolution gene SD1, thus reducing the endogenous GA level in rice. Moreover, OsABF1 interacts with and transcriptionally antagonizes to the polycomb repression complex component OsEMF2b, whose mutant showed as similar but more severe phenotype to OsABF1 overexpression lines. It is suggested that OsABF1 recruits RRC2-mediated H3K27me3 deposition on the SD1 promoter, thus epigenetically silencing SD1 to maintain the GA homeostasis for growth and seed germination. These findings shed new insight into the functions of OsABF1 and regulatory mechanism underlying GA homeostasis in rice.