A rice exocyst subunit gene SEC3A is required for anther dehiscence

Anther dehiscence controls optimal interaction between pollen and stigma,thereby determining the successful sexual reproduction.The regulators or mechanisms of this process remain elusive.Here,two CRISPR/Cas9 mutants of a rice exocyst subunit gene SEC3A,sec3a-1 and sec3a-2,showed anther indehiscence at anthesis and male sterility at maturity.Pollen viability and germination in the mutants were partly defective,whereas their female gametes undergone a normal development.Hybrid or self-pollinated seeds could be produced by artificial pollination,suggesting potential use of a weak sec3a mutant as a female line during hybrid breeding.SEC3A is widely expressed in various tissues,including anther walls.Further results showed an excessive IAA accumulation and no endothecium lignification in sec3a-1/2 anthers.Our findings suggest that SEC3A appears to regulate anther dehiscence by modulating auxin signaling,providing insights into regulation of anther dehiscence and function of exocyst in plants.

R2R3-type Lo MYB21 affects jasmonate-regulated development and dehiscence of anthers in lily(Lilium oriental hybrids)

Lilies are widely cultivated for cut flowers,but their large anthers carry a considerable amount of colored pollen that is dispersed easily.Studying the molecular mechanism of anther development and dehiscence could help solve this problem.LoMYB21,encoding a putative R2R3v-myb avian myeloblastosis viral oncogene homolog(MYB)transcription factor,was identified from oriental lilies(Lilium‘Siberia’).Real-time quantitative PCR analysis showed that LoMYB21 was mainly expressed in the anther,filament and stigma and had high expression during the late stages of lily anther development.LoMYB21 had transactivation activity and was located in the nucleus through yeast one-hybrid assays and transient expression in Nicotiana benthamiana.Suppression of LoMYB21 by virus-induced gene silencing(VIGS)in Lilium‘Siberia’led to anther indehiscence and reduced the expression of genes related to Jasmonate acid(JA)biosynthesis and signal transduction.Induction of LoMYB21 in DEX::LoMYB21 transgenic Arabidopsis caused procumbent inflorescences that became infertile,accompanied by higher expression of JA biosynthetic and signaling genes.These results demonstrated that JA content and signaling were abnormal in silenced lily and transgenic LoMYB21 Arabidopsis,which affected anther development.Our study indicated that LoMYB21 could regulate lily anther dehiscence through JA biosynthesis and signaling during the late stages of anther development.

Anther Dehiscence Disturbed by High Temperature and Water Stress Presented in Os DIR Gene Expression in Rice(Oryza sativa L.)

In future climates, rice could more frequently be subjected to simultaneous high temperature （HT） and water stress （WS） during sensitive developmental stages such as flowering. In this study, two rice genotypes were exposed to HT, WS and combined high temperature and water stress （WS ＋ HT） during flowering to quantify their response through anther dehiscence. Gene expression profiles of 15 selected OsDIRs revealed differences among stresses and between varieties. The targeted gene OsDIR-08, which was considered to be a HT stress candidate gene, was de- creasingly expressed from the 1st d to the 4th d under HT stress in Nagina 22 （N22） while increased in Moroberekan. Varies of the expression of OsDIR genes in stresses intuitively reflects on the lignin-staining at the anther dehisced sites, which implied a negative relationship between the lignin biosynthesis and OsDIRs＇ ex- pression. Anther dehiscence disturbed by HT and WS ＋ HT stress showed a nega- tive cumulative effect in HT sensitive variety Moroberekan but not in N22. Higher level of anther dehiscence in /V22 under HT and WS ＋ HT stress indicated its true tolerance of HT and to WS ＋ HT during anthesis. The differentially expressed of OsDIR（s） under various managed stresses caused the difference of the lignin-stain- ing at the anther dehisced site in N22, and thus transformed anther dehiscence correspondingly might be one of the main reasons for the tolerance.

The regulatory mechanism of rapid lignification for timely anther dehiscence

Anther dehiscence is a crucial event in plant reproduction,tightly regulated and dependent on the lignification of the anther endothecium.In this study,we investigated the rapid lignification process that ensures timely anther dehiscence in Arabidopsis.Our findings reveal that endothecium lignification can be divided into two distinct phases.During Phase Ⅰ,lignin precursors are synthesized without polymerization,while Phase Ⅱ involves simultaneous synthesis of lignin precursors and polymerization.The transcription factors MYB26,NST1/2,and ARF17 specifically regulate the pathway responsible for the synthesis and polymerization of lignin monomers in Phase Ⅱ.MYB26-NST1/2 is the key regulatory pathway responsible for endothecium lignification,while ARF17 facilitates this process by interacting with MYB26.Interestingly,our results demonstrate that the lignification of the endothecium,which occurs within approximately 26 h,is much faster than that of the vascular tissue.These findings provide valuable insights into the regulation mechanism of rapid lignification in the endothecium,which enables timely anther dehiscence and successful pollen release during plant reproduction.