The chloroplast is important organelle responsible for photosynthesis and various bio- synthetic functions essential to green plants. However, the regulatory mechanism of chloroplast development remains elusive. Here, we characterized a mutant with defective chloroplasts in rice (Oryza sativa L.) named it albino and lethal 13(osal13), which exhibited a distinct albino phenotype in leaves, eventually leading to seedling lethality. Molecular cloning revealed that OsAL13 encodes a novel protein in rice for which no homologous gene or known conserved domain was found. Analysis of the biological characteristics showed that the RNAi2 leaf was completely albino phenotype, the root and shoot lengths were significantly inhibited compared with wild type. Transmission electron microscopy indicated that RNAi2 were defective in chloroplast development. Overexpression of OsAL13 resulted the photosynthetic rate increase, So the total grain number per panicle also would be significantly increase. Besides, OsAL13 was located in chloroplast and constitutively expressed in various tissues, including green and non-green tissues. In addition, disruption of OsAL13 resulted in altered expression of plastid-encoded polymerases and nuclear-encoded chloroplast genes, OsAL13 also affected hormone levels in plant tissues. Therefore, our results provide new insights into the role of OsAL13 in regulating chloroplast development in rice.

Photoperiod sensitivity (PS) is the major determinant of flowering time in rice and has played a critical role in adaptation across diverse ecotypes. To dissect the genetic and molecular architecture of PS in MYR landraces, we combined GWAS with transcriptomic profiling on 236 diverse accessions. Thirteen major QTL underlying heading date were mapped on chromosomes 1, 2, 3, 6, 7, and 8, consisting of the previously reported flowering genes (OsHd1, OsFTIP9) and a number of novel loci specific to Myanmar germplasm. Comparative RNA-seq analysis, using a photoperiod-sensitive (V10) and a photoperiod-insensitive (V3) indica genotype to the japonica cultivar ‘H479B’ as reference, showed distinct transcriptional reprogramming in response to short-day conditions, with higher-expression plasticity occurring in V10. By integrating GWAS signals with differential expressions, we narrowed our candidate gene set of two high-confidence regulators: Os06g0275000, encoding a zinc finger transcription factor, and Os07g0606600 (NF-YB10). Both genes were highly expressed in a stage-specific manner and further confirmed by qRT-PCR. Our results suggest a complex genetic regulatory network attracting conserved photoperiod pathways with unique novel allelic variant populations in Myanmar landraces. These candidate genes will be potential targets for precision breeding to optimize flowering time and enhance adaptation both in response to climate change and photoperiodic changes.